Method for analysis of drilling fluids

ABSTRACT

PCT No. PCT/GB93/00406 Sec. 371 Date Jan. 9, 1995 Sec. 102(e) Date Jan. 9, 1995 PCT Filed Feb. 26, 1993 PCT Pub. No. WO93/17326 PCT Pub. Date Sep. 2, 1993.A method of analyzing a drilling fluid comprising subjecting a sample of the fluid to an XRF analysis technique and comparing the results obtained with a calibration model to determine the amount of one or more components of the fluid present in the sample. The method is particularly useful for determining solids in the fluid such as barite and can be combined with an FTIR technique which is sensitive to other components of the fluid. A PLS algorithm is used to construct the model from the spectra.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of analysing drilling fluidsand is particularly useful for the determination of solids in drillingfluids and differentiation between the different types of these solids.

2. Description of the Related Art

During the drilling of an oil or gas well, large volumes of solidscuttings are generated by the drill bit. These solids are conveyed tothe surface by means of circulating drilling fluids, often known as"mud", which are often complicated mixtures of water, oil, soluble andinsoluble minerals, polymers, surfactants and salts. A large portion ofthe drill cuttings can usually be removed from the fluid by means ofvibrating screens and other solids separators, so that after thiscleaning process the fluid can be recirculated down the drill string.However, some of the drill cuttings are dispersed as very smallparticles, which cannot be removed by the solids separation process. Thepresence of these fines, often called "drilled solids" (DS), affects thefunctional properties of the fluid. Determination of the concentrationof DS is particularly complicated by the presence of two other types ofsolids in the fluid, commercial clays and weighting material.

Commercial clays are added to the fluid for control of rheological andfiltration properties. Usually, bentonite or other chemically treatedclay minerals are added for this purpose. The total of commercial clays(CC) and DS is called "low gravity solids" (LGS).

Weighting materials are used to bring the fluid to the required density,necessary to contain underground formation fluids by hydrostaticpressure exerted by the mud column in the annulus. A common weightingmaterial is powdered barite (barium sulfate). The concentration ofweighting materials is known as "high gravity solids" (HGS).

It is important for effective control of the properties of the fluid toknow the individual concentrations of all types of solids. In currentwell site technology LGS and HGS are not measured directly, but arecalculated from the density and solids volume fraction of the drillingfluid, both of which can be measured. The principle of the calculationis that both properties are functions of the volume fractions of LGS andHGS. A simple form of these functions is assumed, and from the resultingset of two simultaneous equations with two unknowns one can readilysolve LGS and HGS. This is usually done by direct calculation or by theuse of charts which may allow for corrections if salts are present.

The total concentration of clays can conveniently be determined at thewell site from their ability to absorb certain cationic dyes. This isthe basis for the well-known methylene blue test, which provides a valueknown as "MBT value" for the concentration of chemically active clays.The larger part of these clays comes usually from the intentionallyadded commercial clays, the remainder is derived from clay minerals inthe drilled solid fraction. If an average proportion of chemicallyactive clays in the drilled solids is assumed, then it is possible tocalculate DS and CC from LGS and MBT.

As mentioned, previously proposed techniques for the determination ofindividual solids concentrations relies on the direct measurement ofdensity and solids volume fraction of the fluid. Density is measuredwith a "mud balance", a well-known rig site device. Solids volumefraction is measured by evaporation of a fluid sample of known volume inan electrically heated distillation apparatus, also well-known as the"mud retort". The liquid distillate is collected in a graduatedreceiver, and from the volume of distillate and the volume of theoriginal fluid sample the volume fraction of total solids is calculated.Problems associated with the use of these two pieces of equipment arethe possibility of an incorrect apparent density as determined by themud balance because of the presence of gas in the fluid sample, andfurther, the fact that the mud retort suffers from errors caused byleaks in the vapour condenser and the inability to accurately introducea known sample volume. Further errors are also caused by the assumptionsenabling solution of the simultaneous equations mentioned previously. Inthis respect a density for the weighting material needs to be assumed.In the case of barite, drilling grade material is in fact a mixture ofpure BaSO4 (specific gravity 4.5) and impurities. The commercial producthas specific gravity 4.20-4.25 at best. Furthermore, the specificgravity of the drilled solids are known with even less certainty.Corrections need to be applied if oil or soluble salts are present inthe fluid. These corrections are also based on measurements with limitedreliability and on not precisely known physical properties. Because onthe large number of measurements and questionable assumptions made inthe current methods, the resulting values for DS and HGS are known to beof limited value. It is, for example, not unusual to find negativenumbers for the concentration of barite, or to find unreasonably highvalues for the drilled solids content.

Control of the composition has been recognised as important inmaintaining the desired properties of the drilling fluid and variousmethods have been proposed for monitoring the composition of thedrilling fluid. The ionic composition of the fluid can be analysed usingion chromatography and this can also be used to obtain an indication ofthe cation exchange capacity of the clay materials present. Examples ofthis are found in our copending patents and applications U.S. Pat. No.4,904,603, U.S. Pat. No. 4,878,382 and EP 89203062.8 which areincorporated herein by reference. It has also been found that a morecomplete analysis, including information on both organic and inorganicand mineral composition can be obtained using FFIR. Examples of this canbe found in our copending European and UK patent applications EP90202796.0, EP 90202795.2, and

UK 9107041.7 also incorporated herein by reference. However, all ofthese methods encounter some problem when attempting to determine theamount of solids in a sample, particularly if the size of the solidparticles interferes with the measurements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method foranalysing drilling fluids which allows improved measurement of the solidmaterial contained therein.

The object of the invention is achieved using an X-ray fluorescence(XRF) analysis technique. Although such techniques are well known forgeneral chemical analysis and have even been proposed for the analysisof core samples taken from wellbores (see GB 2,225,110), no suchtechnique is known to exist which enables the accurate determination ofthe composition of drilling fluids.

In EP-A-0067514, which is considered particularly useful for aquantitative borehole analysis of surrounding rock, concentrations ofchemical elements are determined by detecting from the object examinedboth an XRF-signal of an element in question and a Compton scatteringsignal. The analysis of the element follows in essence from acurve-fitting of the ratio of those signals to known elementconcentrations in calibration objects.

According to CA-A-1219688 a potential ore block is irradiated with gammaradiation. The resulting X-ray fluorescence and Compton scattering aredetected, and these two signals are compared with each other, theirratio reflecting the heavy metal content in the block. Rejection of theblock takes place on the basis of the X-ray fluorescence signal toCompton signal ratio, and therefore their ore potential, falling below athreshold value.

In accordance with the broadest aspect of the present invention, thereis provided a method of analysing a drilling fluid comprising solidssuspended in a liquid phase, the method comprising subjecting a sampleof the fluid to an X ray fluorescence analysis technique so as to derivea spectrum therefrom; analysing the spectrum to identify a peak ofintensity I_(HGS) in the spectrum due to the presence of a component ofthe high gravity solids fraction of the sample and a peak of intensityI_(Co) due to Compton scattering and determining the ratio I_(HGS)/I_(Co) ; and using data from the derived spectrum, the ratio I_(HGS)/I_(Co) and a calibration model to calculate the amount of saidcomponent and liquid phase in the sample.

The advantage of using an XRF technique is that it is particularlysensitive to the minerals which comprise the high gravity solids presentin drilling fluids, especially barite. The XRF spectrum will alsocontain some features which are due to components of the fluid which donot themselves have an XRF spectrum but which affect the spectrum ofthose components which do. Consequently, by preparation of a suitablecalibration model it is possible to calculate properties of the fluidsuch as water content, oil and brine content and specific gravity. Ifthe specific gravity of the sample is measured, this can be used toimprove the calculation of the content of the components of the fluid,oil/water ratio, brine density etc. Likewise, the amount of LGS in thesample can be calculated despite the fact that very little of the LGSproduces an XRF spectrum of its own.

Determination of the ratio I_(HGS) /I_(Co) is important since thecomponent peak and the Compton scattering peak both contain informationrelating to the average atomic number Z of the sample which can becalculated from the ratio of the two. It is preferred that the methodinvolves irradiating the sample with radiation which provides a strongsignal due to the presence of barium or, if any other weighting materialis present, a constituent of the weighting material. It has been foundparticularly advantageous to monitor the L.sub.α and L_(k)α lines of thebarium spectrum when determining the concentration of barite.

The determination of the concentration of barium in whole mud samples islinked through the simple chemical constitution of barite to theconcentration of HGS in the mud. Hence, having an accurate measurementof HGS constitutes an improvement over the conventional techniques formud solids measurement, which rely on the retort and the mud balanceand, as described before, require the determination of two unknowns, HGSand LGS, from a set of two simultaneous equations. For example, LGS canbe found from:

    LGS=1.667 W-1.296 HGS-1.667

where LGS and HGS are concentrations in g/L, and W is the mud density inkg/L. HGS is now the concentration of barite, directly determinedaccording to the invention although it will be appreciated that otherrelationships might also be used.

In a further aspect of the present invention, there is provided a methodof determining the concentration of polymer in drilling fluidscomprising analysing the mineral concentrations in a sample by XRF andusing the thus determined mineral concentrations to calibrate the IRspectrum of the sample with respect to the mineral components andanalysing said spectrum with respect to the polymers.

Measurement of organic components in mud by FTIR, typically using thePLS technique is often difficult because they are present in smallquantities. The spectra are dominated by mineral components which areusually present in larger quantities yet calibration is hampered by thefact that the minerals often do not have well deemed spectra as theyhave a variable, mixed composition, as witnessed for example by thelarge number of clay minerals occurring in sediments. The application ofthis aspect of the invention consists of determining at least barite byXRF and importing this information, as non-spectral information, into asuitable FTIR calibration model. In the case of weighted muds, thisinformation would determine to some extent the composition of the mud,and one source of uncertainty is removed from the input data set. As aresult the prediction of trace components, such as organics is improved.A further extension of this idea is to input the Ca-LGS and non-Ca-LGSas determined by XRF as weB. Again this should help in resolving some ofthe difficulties experienced by the PLS algorithm caused by ill-definedFTIR spectral features.

A single element technique based upon measurement of the intensity ofthe barium fluorescence line or lines is potentially applicable to thepresent invention. In the case of typical drilling mud formulations theconcentrations of barite can be sufficiently high to cause significantnon-linearity of the curve relating barium fluorescence intensity tobarite concentration. As concentrations of barite increase, selfabsorption of the fluorescence by barium becomes more important, untilthe fluorescence signal saturates. However, in practical drilling mudformulations, saturation is not reached over the range of possiblebarium concentrations. In addition to self absorption, attenuation andscattering of the fluorescence radiation by the matrix plays also arole. This matrix effect can generally be corrected for in quantitativeXRF spectrometry if analyte concentrations are low and the matrix has aknown density or composition. Under these conditions count rate I_(Ba)of the fluorescence peak for barite is proportional to bariumconcentration [Ba]:

    I.sub.Ba =s[Ba]

The sensitivity of the measurement, s, is inversely proportional to themass absorption coefficient μ/ρ: ##EQU1## where μ/ρ itself is roughlyproportional to the third power of the average atomic number Z:

    μ/ρ=K.sub.2 Z.sup.3

Hence, one finds that the barium count rate is strongly dependent on Z³: ##EQU2##

The basis for a number of conventional algorithms consists of relaxingthis strong matrix dependency by division of the barium count rate by abackground count rate, which is approximately inversely proportional toZ². It is convenient to take for the background reading the area of theCompton scattering (incoherent scattering peak), I_(Co), so that##EQU3## which leads to ##EQU4## where X is the ratio between bariumfluorescence and Compton scattering count rates.

At concentrations of barium that are common in mud engineering, thislinear relation between X and [Ba] breaks down and can be replaced by,for example, a power series such as:

    [Ba]=b.sub.0 +b.sub.1 X+b.sub.2 X.sup.2 +b.sub.3 X.sup.3

or by a hyperbolic function such as ##EQU5##

In both examples the empirical coefficients b₀, etc. and A,B,C aredetermined from calibration samples containing known amounts of barium.In this empirical approach an attempt is made to use Compton scattering,which has been shown to be inversely proportional to the mass absorptioncoefficient, as a means to eliminate the matrix effect; using the samesymbols as before one have ##EQU6##

The potential problem with the single element method is that empiricalcalibration methods based on the relationship ##EQU7## will have onlylimited success if Z varies from sample to sample and is not known.

A fundamental problem in mud engineering is that the matrix of drillingmud samples is variable as a result of contamination with formationminerals and the presence in unknown amounts of mud chemicals. Thus,some of the elements other than barium that may be present inappreciable variable quantities are S, Cl, K and Ca., and also Cr andother transition metals. This means that the average Z, which influencesthe relation between [Ba] and the count ratio X, is unknown. Theconsequences of this uncertainty can cause errors when muds containingthe interferences were measured using calibration coefficients derivedfrom calibration sets of muds not containing the interference. Tocircumvent the matrix problem, a large number of calibrations could bemade from which one would be selected on the basis of chemical knowledgeof the sample, for example the calcium content. However, care must betaken to avoid undesirable degrees of complication, arbitrariness, andoperator dependency. It is also difficult to achieve one singlecalibration model to describe a wide range of barite concentrations, sothat overlapping calibration models can be avoided. When using theempirical correlations such as (power series) and (hyperbolic relation),there often remains some curvature of a plot of actual versus predictedconcentrations.

In one method which could overcome the problem of variable Z is to inputZ (average atomic number of the sample) with the calibration samples asa non spectral attribute in a PLS regression technique. This wouldcreate a calibration model ("PLS+Z") where the Z is necessary as aninput, along with the XRF data. The measurement of an unknown would thengo in two stages. In the first stage one measures it with a calibrationmodel that does not require Z ("PLS w/o Z"). This would give anapproximate value for the elements Cl, K, Ca, Ba, from which onereconstructs the average chemical composition of the sample, from whichZ is computed. In the second stage the spectral data plus the justcalculated Z is input into the "PLS+Z" model and a better accuracyshould result. The process may need to be reiterated to converge onconstant composition.

Frequent recalibration is required to compensate for machine drift,which requires large numbers of calibration samples. Thus, in order toobtain sufficiently accurate values for the calibration coefficientsb_(i) in the power series equation, typically about 10 calibrationsamples have to be presented to the analyser and the coefficientscalculated by a regression technique e.g. PLS. The input data used inthis calibration process and also in the subsequent determination ofbarite in unknowns is the ratio X, determined from pre-set windowsspanning the barium fluorescence and Compton scatter peaks. Ideally thecalibration sample set should consist of simulated muds, in order to letthe analyser see the correct matrix. But it is impractical to store mudsamples for the longer times required, as they require frequent mixingto avoid settling of a thin barite layer on the bottom of the samplecells, which would completely distort the analysis. Hence the samplesneed to be stored in separate stirred containers and poured out into thesample cells before calibration. This makes the technique in fieldpractice prone to errors (caused for example by unintended crosscontamination between samples). Alternatively solids samples could beconstructed from barite and some fixation agent (glass, resin, etc.).The problem with this solution is the different matrix, which precludesuse of the Compton peak. Finally, a durable solid reference sample couldbe used to restandardise the analyser before measurement of unknowns,but over periods of months sufficient line broadening of the bariumfluorescence occurs to invalidate earlier calibrations, since theCompton peak does not change in time at the same rate as thefluorescence peak, and therefore the ratio X is not constant in time.Thus, the single element approach via empirical correlations describedabove can have practical drawbacks when used on a drilling rig.

A solution to practical problems associated with the single elementtechnique described above is to use more spectral information inaddition to the spectrum produced from a single source (usually Am 241), and to use the information from all individual channels of amultichannel analyser. With this technique barite can be determined withgreatly improved accuracy compared with the single element methodsstudied.

There is also sufficient information to calculate LGS, SG, etc. and forthis purpose one uses a second source, such as Fe 55, typically with asealed Ne/CH4 detector. This source allows K line fluorescence peaks tobe observed from S, Cl, K, Ca, Cr, and the L-α peak from Ba. All ofthese peaks overlap. Since calibration of this system would be verycomplicated, a regression technique is utilised, Partial Least Squares(PLS), developed by Wold et al. Suitable windows in the spectral dataare selected and the PLS calibration technique is presented withspectral data from a large set of calibration muds. To obtain acceptableaccuracy it is necessary to do some preprocessing of the spectral databy means of expressions similar to the ratio I_(Ba) /I_(Co), discussedabove. Generally, individual channels are used instead of summations ofchannels. The PLS technique requires large numbers of calibrationsamples, depending on the number of components in the samples.

It is advantageous to use two sources which have different responses tothe components of the mud under analysis. In the case described above,the Am 241 source provides a signal which can be used to obtain anindication of the Ba content of the sample. Ba also contributes to thesignal from the Fe 55 source and so the estimation of the Fe 55 signalcontribution from Ba can be improved by inputting the Am 241 estimationof the Ba content into the PLS algorithm as applied to the Fe 55 signal.This in turn improves the estimation of the other mud components fromthe Fe 55 signal since the Am 241 Ba estimation is in effect an internalcalibration for that sample. Thus the output from the PLS analysis ofthe signals from both sources provides an estimation of Ba, Ca, K, Cl,LGS, H₂ O, specific gravity (SG) and average atomic number (Z). Theestimate of SG and Z can then be taken and applied to PLS analysis ofthe same data as non-spectral attributes which will allow improvedestimation of Ba, Ca and K. In an alternative case, SG is measuredseparately and is input into the PLS algorithm as a non-spectralattribute which will improve the measurements further but does requirean extra measurement.

The time taken for that preparation and measurement of the calibrationsamples is often such that appreciable drift of the analyser can takeplace during the calibration phase. This is potentially a severelimitation to accuracy achieved when the calibration is used at a laterstage to determine concentrations of unknowns. It is therefore essentialto correct for any a drift in the calibration and measurement procedure.

Analyser drift is caused by decay of the source and is significant onlyfor an Fe 55 source. More important is drift of the sealed detectors,which is a combination of two ageing phenomena. In the first a gradualdecay of count rates is noted in which the output from each channel ofthe multichannel analyser decreases over time when standard samples aremeasured. The second phenomenon is deterioration of resolution, which isnoted as peak spreading. As a result of peak spreading the rate by whichindividual channels decrease their output depends on the significancethey have for the analysis. For example, the barium fluorescence peakspresent in the Am 241 spectrum are quite sharp. The maxima of thesepeaks decrease in time, but the fringes rise. Hence to correct for driftin this spectral region, each channel of the unknown sample needs to bemultiplied by a different appropriate correction factor which isdetermined from measurement of a suitable standard sample. Alternativelyall channels covering the peaks concerned could be summed, but thiswould in time cause some of the peaks' energy to spread beyond theboundaries of the summation interval. It has also been found that theaccuracy of measurement improved by treating individual channelsseparately. As described here the drift correction procedure serves toguarantee continuity between the time a calibration model is constructedand the time an unknown sample is analysed.

A second practical advantage of drift correction is that it allows onecalibration model to be transferred between different analysers. Becauseof the ageing process, the detectors will generally exhibit a differentdegree of resolution. By measurement of suitable standard samples theappropriate correction factors for individual channels can be found,allowing a calibration model to be used that was constructed on adifferent analyser.

A third use of drift measurements is provision of a warning mechanismfor unusual conditions of the analyser. The decay characteristics of thedetector performance were found to obey an exponential decay law.Occasionally individual measurements on standard samples can be welloutside the statistically expected range, and this could be correlatedby events such as periods of idleness of the analyser, transportation,or climatic differences. The system needed then to adjust to changedconditions and during the adjustment period discrepancies could occurbetween measurements made shortly after each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described by way of example, withreference to the accompanying drawings, in which:

FIGS. 1-16 show plots for calibration and validation of a model tointerpret the results of the method according to the present invention;and

FIGS. 17 and 18 show XRF spectra of a drilling mud obtained using Am 241and Fe 55 sources respectively, energy increases from left to fight,count rate is plotted vertically.

DESCRIPTION OF THE PREFERRED EMBODIMENT EXAMPLES

In the following examples, the system described below was used both as alaboratory test environment and as a system which could be applied to arig environment. The system uses the Lab-X 1000 (Oxford AnalyticalInstruments), a portable (20 kg) energy dispersive spectrometer, fittedfor our purposes with an Am 241 gamma-ray source and sealed proportionalcounter, filled with Xe/CH₄ and an Fe 55 source with a sealed counterfilled with Ne/CH₄. This combination provides the K-α and K-βfluorescence peaks from barium in addition to a well defined Comptonscatter peak to account for matrix effects and K line fluorescence peaksfor S, Cl, K, Ca, Cr and the Lα peak for B_(a). The spectrum obtainedfrom the Am 241 source is shown in FIG. 17 and as can be seen isdominated by the Ba (K) peak with a significant Compton scattering peakCo. The spectrum from the Fe 55 source shows several overlapping peaksincluding the Ba (L) peak which is found in part at the high energy endof the spectrum. Because the Ba peak for the Am 241 source does notinvolve significant interferences, a reasonable estimate can be obtainedfor Ba concentration from this spectrum using a PLS algorithm. Thisestimate can then be used in the PLS algorithm applied to the Fe 55spectrum since it will provide a good estimation of the contribution ofthe Ba (L) peak to the spectrum and so allow better estimation of theother unknowns. Once the Fe 55 spectrum is analysed, an estimation of Zand possibly SG can be obtained which can in turn be applied to a newPLS algorithm to analyse the Am 241 spectrum a second time.

The technique necessary for using XRF for analysis of drilling mudincludes the following steps.

(1) A large number of data points selected from the spectral informationis obtained. The Lab-X 1000 uses a 256 channel multichannel analyser.Windows containing the Ba K lines and the Compton peak from the Am 241spectrum are isolated and their ratios determined. All data points fromthe Fe 55 spectrum are used, starting with the S fluorescence. Someratioing of spectral information is done.

(2) The calcium concentration in the mud filtrate is determined in theconventional manner by EDTA titration. For oil based muds the oil /water volume ratio is determined. In the case of calibration samples,this information is known from the make-up of the sample. All of thisinformation, together with the mud density, is input into the PLSalgorithm, with the spectral information prepared as per the previousstep.

(3) In the calibration stage steps (1) and (2) are repeated for each ofthe calibration samples, and the composition of each of the samples isinput into the PLS algorithm. Suitable compositional categories are:barite, LGS not containing Ca., LGS containing Ca, soluble K, Cl, watercontent, oil content The PLS algorithm is then run to produce acalibration model.

(4) In the prediction phase unknowns are run by the XRF analyser anddensity, oil/water ratio and soluble calcium are input into thecalibration model. The following compositional information is thenproduced: barite, LGS not containing Ca, LGS containing Ca, soluble K,Cl, water content, oil content.

Table 1 below shows the compositions of a series of calibration sampleswhich were used to construct a calibration model using the PLSalgorithm. Table 2 shows the compositions of the samples used tovalidate the calibration model. The results of the calibration step forBa,Ca,K,Cl, LGS, H₂ O,Z and SG are shown in Tables 3-10 and FIGS. 1-8.Tables 11-18 and FIGS. 9-16 show the results of the prediction ofBa,Ca,K,Cl, LGS, H₂ O,Z and SG for the samples in the validation setusing the calibration model. In the various examples, predictions havebeen made with the various models summarised below. These can be dividedinto two main groups, those which have SG (mud density) input into themodel and those which have no input of SG. Obviously, the prediction ofSG can only use a model which does not have SG as an input.

DESCRIPTION OF CALIBRATION MODELS USED IN THE EXAMPLE

Input elements

H1=a set of individual channels in the Fe 55 spectrum comprising the Cl,K, Ca, and Ba(L) peak areas.

H2=a set of individual channels in the Am 241 spectrum comprising theBA(K) and Co peak areas

Ba/Co=the summation of the channels containing the Ba(K) peak areadivided by the summation of the channels containing the Co peak area.The first, second and third powers of this ratio are input.

Z=the average atomic weight of the sample. Calculated for thecalibration samples from weight fractions and molecular formulae ofcomponents making up the sample or predicted by Model P1 in the case ofvalidation samples and unknowns. The first, second and third powers of Zare input.

SG=the density of the sample. Calculated for the calibration samplesfrom weight fractions and densities of components making up the sample.In the case of validation samples and unknowns SG as an input ispredicted by Model P1 or is obtained by direct measurement. The first,second and third powers of SG are input

Composition of models in terms of input elements

In the table X indicates that a particular input element is present.

    ______________________________________                                        Model name H1       H2    Ba/Co    Z   SG                                     ______________________________________                                        P1                  X     X                                                   PA                        X        X   X                                      P2         X              X                                                   PR01       X              X        X   X                                      PE                        X            X                                      PG         X              X            X                                      ______________________________________                                    

Outputs

In the Table X indicates that a particular output is predicted by themodels listed; X* indicates the preferred way of prediction of anoutput.

    ______________________________________                                        Model                                                                         name  Ba     Cl     K    Ca   LGS   H2O   Z    SG                             ______________________________________                                        P1    X                       X     X     X*   X                              PA    X*                      X     X                                         P2    X      X*     X    X    X*    X*    X    X*                             PR01  X      X      X*   X*   X     X                                         PE    X*                      X     X     X*                                  PG    X      X*     X*   X*   X*    X*    X                                   ______________________________________                                    

Combinations of calibration models

If density is used as an input then the two models PE and PG will serveto provide all outputs.

If density is not used as an input then a two stage process is followed.In the first stage Models P1 and P2 provide predicted values for Z andSG. Barite is produced in the second stage by Model PA, which uses thepredicted Z and SG as inputs. Similarly K and Ca are produced by ModelPR01. Values for Cl, LGS and H2O are taken directly from the predictionby Model P2 in the first stage.

    __________________________________________________________________________    SUMMARY OF CORRELATION COEFFICIENTS                                           Models Predicting Density                                                                             Models using Density as Input                         Component   Calibration                                                                         Validation  Calibration                                                                         Validation                                (Property)                                                                          Model no.                                                                           corr. coeff.                                                                        corr. coeff.                                                                        Model no.                                                                           corr. coeff.                                                                        corr. coeff.                              __________________________________________________________________________    Barite                                                                              PA    0.999 0.998 PE    0.999 0.999                                     Chloride                                                                            P2    0.917 0.954 PG    0.892 0.947                                     Potassium                                                                           PR01  0.953 0.952 PG    0.894 0.943                                     Calcium                                                                             PR01  0.946 0.873 PG    0.911 0.895                                     Water P2    0.979 0.958 PG    0.981 0.991                                     LGS   P2    0.974 0.937 PG    0.985 0.980                                     Z     P1    0.999 0.998 PE    0.996 0.998                                     SG    P2    0.989 0.981                                                       __________________________________________________________________________

                                      TABLE 1                                     __________________________________________________________________________    CONCENTRATIONS (gl): Calibration set                                          SAMPLE                                                                              BaSO.sub.4                                                                         CaCO.sub.3                                                                        KNO.sub.3                                                                         KCL NaCL                                                                              H.sub.2 O                                                                         POLYMER                                        __________________________________________________________________________     1    3.19 3.47                                                                              37.12                                                                             0.00                                                                              75.16                                                                             954.43                                                                            7.5                                             2    5.79 1.52                                                                              6.71                                                                              0.00                                                                              16.29                                                                             979.71                                                                            7.5                                             4    10.34                                                                              0.60                                                                              2.39                                                                              0.00                                                                              31.13                                                                             986.87                                                                            7.5                                             5    16.48                                                                              167.60                                                                            3.11                                                                              0.00                                                                              9.90                                                                              926.38                                                                            7.5                                             7    27.54                                                                              63.11                                                                             0.00                                                                              160.46                                                                            5.99                                                                              897.65                                                                            7.5                                             8    31.57                                                                              250.58                                                                            8.34                                                                              0.00                                                                              107.97                                                                            852.49                                                                            7.5                                            10    44.07                                                                              93.38                                                                             0.00                                                                              91.32                                                                             91.88                                                                             885.14                                                                            7.5                                            11    55.20                                                                              280.64                                                                            0.60                                                                              0.00                                                                              17.36                                                                             874.56                                                                            7.5                                            13    76.76                                                                              178.26                                                                            10.30                                                                             0.00                                                                              87.58                                                                             882.31                                                                            7.5                                            14    83.62                                                                              81.62                                                                             26.94                                                                             0.00                                                                              48.22                                                                             915.91                                                                            7.5                                            16    101.62                                                                             140.70                                                                            0.00                                                                              190.71                                                                            11.89                                                                             841.29                                                                            7.5                                            17    107.61                                                                             22.95                                                                             1.92                                                                              0.00                                                                              15.01                                                                             959.50                                                                            7.5                                            19    126.05                                                                             198.45                                                                            95.71                                                                             0.00                                                                              144.61                                                                            796.48                                                                            7.5                                            20    136.11                                                                             130.28                                                                            5.11                                                                              0.00                                                                              28.46                                                                             897.72                                                                            7.5                                            22    162.65                                                                             221.24                                                                            51.81                                                                             0.00                                                                              220.44                                                                            774.88                                                                            7.5                                            23    170.00                                                                             147.09                                                                            72.05                                                                             0.00                                                                              89.21                                                                             842.61                                                                            7.5                                            26    211.15                                                                             227.11                                                                            8.90                                                                              0.00                                                                              44.23                                                                             841.96                                                                            7.5                                            28    247.59                                                                             155.43                                                                            0.00                                                                              41.71                                                                             203.76                                                                            794.38                                                                            7.5                                            29    258.04                                                                             115.55                                                                            0.00                                                                              173.62                                                                            78.03                                                                             746.03                                                                            7.5                                            31    290.69                                                                             15.37                                                                             7.18                                                                              0.00                                                                              11.38                                                                             911.35                                                                            7.5                                            32    308.73                                                                             89.73                                                                             68.93                                                                             0.00                                                                              71.65                                                                             832.68                                                                            7.5                                            34    347.21                                                                             106.53                                                                            1.72                                                                              0.00                                                                              248.27                                                                            789.62                                                                            7.5                                            35    352.97                                                                             77.95                                                                             104.90                                                                            0.00                                                                              109.97                                                                            799.86                                                                            7.5                                            37    386.38                                                                             283.72                                                                            4.71                                                                              0.00                                                                              79.63                                                                             772.99                                                                            7.5                                            38    399.65                                                                             184.80                                                                            0.92                                                                              0.00                                                                              149.60                                                                            741.59                                                                            7.5                                            40    432.98                                                                             58.47                                                                             35.48                                                                             0.00                                                                              36.32                                                                             851.16                                                                            7.5                                            41    448.96                                                                             36.84                                                                             0.00                                                                              114.28                                                                            130.64                                                                            787.44                                                                            7.5                                            43    486.32                                                                             203.88                                                                            113.28                                                                            0.00                                                                              123.54                                                                            714.11                                                                            7.5                                            44    510.11                                                                             172.15                                                                            129.32                                                                            0.00                                                                              137.71                                                                            707.61                                                                            7.5                                            46    545.59                                                                             67.26                                                                             89.73                                                                             0.00                                                                              96.99                                                                             776.42                                                                            7.5                                            47    551.93                                                                             208.95                                                                            0.00                                                                              182.85                                                                            22.35                                                                             707.88                                                                            7.5                                            49    571.69                                                                             229.74                                                                            6.19                                                                              0.00                                                                              10.90                                                                             772.33                                                                            7.5                                            50    591.24                                                                             49.09                                                                             0.32                                                                              0.00                                                                              19.36                                                                             830.92                                                                            7.5                                            52    633.84                                                                             112.80                                                                            54.80                                                                             0.00                                                                              62.07                                                                             768.51                                                                            7.5                                            53    650.74                                                                             138.90                                                                            0.00                                                                              68.17                                                                             155.59                                                                            707.85                                                                            7.5                                            55    697.11                                                                             276.85                                                                            0.00                                                                              142.10                                                                            53.29                                                                             651.52                                                                            7.5                                            56    722.76                                                                             267.54                                                                            44.70                                                                             0.00                                                                              84.14                                                                             684.56                                                                            7.5                                            58    758.48                                                                             33.37                                                                             49.41                                                                             0.00                                                                              171.87                                                                            727.95                                                                            7.5                                            59    778.25                                                                             259.40                                                                            119.66                                                                            0.00                                                                              147.24                                                                            623.27                                                                            7.5                                            61    823.79                                                                             135.11                                                                            18.56                                                                             0.00                                                                              228.07                                                                            664.30                                                                            7.5                                            62    843.51                                                                             25.07                                                                             137.86                                                                            0.00                                                                              103.58                                                                            645.81                                                                            7.5                                            64    888.54                                                                             238.65                                                                            42.51                                                                             0.00                                                                              92.00                                                                             659.27                                                                            7.5                                            65    908.86                                                                             44.51                                                                             2.00                                                                              0.00                                                                              222.65                                                                            684.30                                                                            7.5                                            68    981.42                                                                             117.95                                                                            60.39                                                                             0.00                                                                              77.23                                                                             672.20                                                                            7.5                                            70    1027.54                                                                            13.49                                                                             0.00                                                                              134.43                                                                            93.76                                                                             669.19                                                                            7.5                                            71    1048.68                                                                            293.69                                                                            121.66                                                                            0.00                                                                              99.39                                                                             559.80                                                                            7.5                                            73    1099.62                                                                            102.02                                                                            2.79                                                                              0.00                                                                              12.25                                                                             700.57                                                                            7.5                                            74    1129.96                                                                            72.76                                                                             66.26                                                                             0.00                                                                              156.06                                                                            611.56                                                                            7.5                                            75    1176.57                                                                            272.97                                                                            74.04                                                                             0.00                                                                              177.34                                                                            532.17                                                                            7.5                                            77    1206.01                                                                            18.16                                                                             20.56                                                                             0.00                                                                              168.64                                                                            646.01                                                                            7.5                                            79    1256.44                                                                            192.31                                                                            39.24                                                                             0.00                                                                              195.78                                                                            548.07                                                                            7.5                                            80    1276.45                                                                            59.99                                                                             3.31                                                                              0.00                                                                              8.70                                                                              676.66                                                                            7.5                                            82    1320.36                                                                            287.02                                                                            7.38                                                                              0.00                                                                              12.89                                                                             584.06                                                                            7.5                                            83    1356.87                                                                            56.20                                                                             0.00                                                                              61.19                                                                             155.86                                                                            583.58                                                                            7.5                                            85    1412.27                                                                            163.45                                                                            0.00                                                                              197.77                                                                            30.45                                                                             472.58                                                                            7.5                                            88    1531.75                                                                            217.05                                                                            9.58                                                                              0.00                                                                              174.43                                                                            474.06                                                                            7.5                                            89    1566.38                                                                            104.50                                                                            0.00                                                                              122.88                                                                            45.50                                                                             538.00                                                                            7.5                                            __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    CONCENTRATIONS (g/l): Validation set                                          SAMPLE                                                                              BaSO.sub.4                                                                         CaCO.sub.3                                                                        KNO.sub.3                                                                         KCL NACL                                                                              H.sub.2 O                                                                         POLYMER                                        __________________________________________________________________________     9    38.32                                                                              17.28                                                                             3.91                                                                              0.00                                                                              4.11                                                                              974.34                                                                            7.5                                            12    67.30                                                                              123.33                                                                            64.28                                                                             0.00                                                                              193.18                                                                            837.04                                                                            7.5                                            18    119.46                                                                             235.41                                                                            46.70                                                                             0.00                                                                              179.53                                                                            787.59                                                                            7.5                                            21    154.39                                                                             109.09                                                                            13.69                                                                             0.00                                                                              237.4                                                                             816.96                                                                            7.5                                            24    183.72                                                                             7.90                                                                              86.13                                                                             0.00                                                                              121.86                                                                            869.09                                                                            7.5                                            27    226.63                                                                             248.19                                                                            0.00                                                                              148.40                                                                            36.12                                                                             776.21                                                                            7.5                                            30    273.21                                                                             20.48                                                                             22.67                                                                             0.00                                                                              128.92                                                                            875.48                                                                            7.5                                            33    323.82                                                                             214.06                                                                            0.00                                                                              58.27                                                                             170.03                                                                            748.71                                                                            7.5                                            36    363.80                                                                             42.43                                                                             7.86                                                                              0.00                                                                              131.72                                                                            846.63                                                                            7.5                                            39    424.81                                                                             7.58                                                                              58.47                                                                             0.00                                                                              100.50                                                                            835.05                                                                            7.5                                            42    466.99                                                                             98.31                                                                             3.59                                                                              0.00                                                                              7.30                                                                              850.61                                                                            7.5                                            48    559.20                                                                             29.54                                                                             144.69                                                                            0.00                                                                              115.55                                                                            752.55                                                                            7.5                                            51    615.48                                                                             126.65                                                                            2.59                                                                              0.00                                                                              5.19                                                                              809.19                                                                            7.5                                            54    678.47                                                                             242.80                                                                            28.34                                                                             0.00                                                                              233.70                                                                            651.85                                                                            7.5                                            57    740.92                                                                             187.29                                                                            10.70                                                                             0.00                                                                              182.81                                                                            690.71                                                                            7.5                                            60    797.00                                                                             159.58                                                                            11.38                                                                             0.00                                                                              13.57                                                                             743.39                                                                            7.5                                            63    867.67                                                                             254.06                                                                            0.00                                                                              177.42                                                                            85.14                                                                             595.21                                                                            7.5                                            66    930.02                                                                             85.21                                                                             4.19                                                                              0.00                                                                              25.74                                                                             738.27                                                                            7.5                                            69    1000.86                                                                            76.16                                                                             5.91                                                                              0.00                                                                              82.22                                                                             709.60                                                                            7.5                                            72    1076.88                                                                            206.08                                                                            0.00                                                                              167.76                                                                            52.61                                                                             587.10                                                                            7.5                                            75    1152.46                                                                            176.14                                                                            0.00                                                                              72.98                                                                             131.44                                                                            584.71                                                                            7.5                                            78    1231.05                                                                            96.39                                                                             12.37                                                                             0.00                                                                              14.29                                                                             671.62                                                                            7.5                                            81    1297.94                                                                            8.30                                                                              25.27                                                                             0.00                                                                              24.08                                                                             590.14                                                                            7.5                                            84    1385.47                                                                            151.79                                                                            149.99                                                                            0.00                                                                              126.12                                                                            514.11                                                                            7.5                                            87    1495.00                                                                            128.33                                                                            102.30                                                                            0.00                                                                              140.42                                                                            510.87                                                                            7.5                                            __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________             mud density not used                                                                          mud density input                                    BARITE        Model PA        Model PE                                        Sample                                                                            Actual                                                                             Pred.                                                                              Error, g/L                                                                          Error, %                                                                           Pred.                                                                              Error, g/L                                                                          Error, %                                  __________________________________________________________________________     1  3.2  5.7  2.5   79.8 9.0  5.8   180.6                                      2  5.8  2.5  -3.3  -57.2                                                                              5.7  -0.1  -1.0                                       4  10.3 7.0  -3.4  -32.7                                                                              10.6 0.3   2.8                                        5  16.5 18.4 1.9   11.8 22.3 5.8   35.1                                       7  27.5 37.9 10.4  37.8 33.8 6.3   22.9                                       8  31.6 44.8 13.2  42.0 48.1 16.5  52.3                                      10  44.1 52.4 8.4   19.0 50.6 6.5   14.7                                      11  55.2 55.0 -0.2  -0.4 57.8 2.6   4.7                                       13  76.8 76.1 -0.7  -0.9 78.2 1.5   1.9                                       14  83.6 78.8 -4.8  -5.8 80.8 -2.8  -3.4                                      16  101.6                                                                              112.9                                                                              11.2  11.1 107.2                                                                              5.6   5.5                                       17  107.6                                                                              94.5 -13.1 -12.2                                                                              95.9 -11.7 -10.9                                     19  126.1                                                                              132.0                                                                              5.9   4.7  133.5                                                                              7.5   5.9                                       20  136.1                                                                              126.7                                                                              -9.4  -6.9 127.5                                                                              -8.6  -6.3                                      22  162.7                                                                              169.7                                                                              7.1   4.3  170.4                                                                              7.7   4.8                                       23  170.0                                                                              163.5                                                                              -6.5  -3.8 164.5                                                                              -5.5  -3.3                                      26  211.2                                                                              202.6                                                                              -8.6  -4.1 203.8                                                                              -7.4  -3.5                                      28  247.6                                                                              240.2                                                                              -7.4  -3.0 235.4                                                                              -12.2 -4.9                                      29  258.0                                                                              271.2                                                                              13.2  5.1  259.1                                                                              1.0   0.4                                       31  290.7                                                                              284.3                                                                              -6.4  -2.2 283.9                                                                              -6.8  -2.3                                      32  308.7                                                                              307.9                                                                              -0.9  -0.3 309.9                                                                              1.1   0.4                                       34  347.2                                                                              332.0                                                                              -15.3 -4.4 326.6                                                                              -20.6 -5.9                                      35  353.0                                                                              351.6                                                                              -1.4  -0.4 353.0                                                                              0.1   0.0                                       37  386.4                                                                              362.8                                                                              -23.6 -6.1 359.3                                                                              -27.1 -7.0                                      38  399.7                                                                              405.9                                                                              6.2   1.6  403.7                                                                              4.1   1.0                                       40  433.0                                                                              421.3                                                                              -11.7 -2.7 419.2                                                                              -13.7 -3.2                                      41  449.0                                                                              453.5                                                                              4.5   1.0  446.4                                                                              -2.5  -0.6                                      43  486.3                                                                              485.2                                                                              -1.1  -0.2 488.0                                                                              1.7   0.3                                       44  510.1                                                                              511.6                                                                              1.4   0.3  514.7                                                                              4.6   0.9                                       46  545.6                                                                              545.3                                                                              -0.3  -0.1 547.2                                                                              1.6   0.3                                       47  551.9                                                                              562.7                                                                              10.8  1.9  556.6                                                                              4.7   0.8                                       49  571.7                                                                              552.6                                                                              -19.1 -3.3 549.9                                                                              -21.8 -3.8                                      50  591.2                                                                              613.6                                                                              22.4  3.8  618.6                                                                              27.3  4.6                                       52  633.8                                                                              636.0                                                                              2.2   0.3  639.6                                                                              5.8   0.9                                       53  650.7                                                                              658.6                                                                              7.9   1.2  656.6                                                                              5.9   0.9                                       55  697.1                                                                              705.4                                                                              8.3   1.2  701.8                                                                              4.7   0.7                                       56  722.8                                                                              733.9                                                                              11.2  1.5  743.8                                                                              21.0  2.9                                       58  758.5                                                                              770.8                                                                              12.3  1.6  774.6                                                                              16.3  2.1                                       59  778.3                                                                              773.0                                                                              -5.3  -0.7 776.5                                                                              -1.7  -0.2                                      61  823.6                                                                              814.9                                                                              -8.8  -1.1 812.1                                                                              -11.7 -1.4                                      62  843.5                                                                              839.6                                                                              -3.9  -0.5 828.8                                                                              -14.7 -1.7                                      64  888.5                                                                              888.7                                                                              0.2   0.0  895.7                                                                              7.1   0.8                                       65  908.9                                                                              902.2                                                                              -6.6  -0.7 897.2                                                                              -11.6 -1.3                                      68  981.4                                                                              987.4                                                                              5.9   0.6  993.4                                                                              12.0  1.2                                       70  1027.5                                                                             1032.7                                                                             5.2   0.5  1024.1                                                                             -3.4  -0.3                                      71  1048.7                                                                             1029.0                                                                             -19.7 -1.9 1028.4                                                                             -20.3 -1.9                                      73  1099.6                                                                             1117.4                                                                             17.8  1.6  1127.1                                                                             27.5  2.5                                       74  1130.0                                                                             1126.7                                                                             -3.3  -0.3 1126.2                                                                             -3.8  -0.3                                      76  1176.6                                                                             1195.4                                                                             18.8  1.6  1207.6                                                                             31.0  2.6                                       77  1206.0                                                                             1206.0                                                                             0.0   0.0  1208.2                                                                             2.2   0.2                                       79  1256.4                                                                             1273.7                                                                             17.3  1.4  1285.2                                                                             28.8  2.3                                       80  1276.5                                                                             1258.2                                                                             -18.3 -1.4 1252.8                                                                             -23.7 -1.9                                      82  1320.4                                                                             1317.4                                                                             -3.0  -0.2 1327.7                                                                             7.3.  0.6                                       83  1358.9                                                                             1331.0                                                                             -25.9 -1.9 1318.2                                                                             -38.7 -2.8                                      85  1412.3                                                                             1428.8                                                                             16.5  1.2  1417.3                                                                             5.0   0.4                                       88  1531.8                                                                             1532.2                                                                             0.5   0.0  1533.0                                                                             1.3   0.1                                       89  1566.4                                                                             1554.9                                                                             -11.5 -0.7 1549.1                                                                             -17.3 -1.1                                      __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________            mud density not used                                                                            mud density input                                   CALCIUM     Model PR01        Model PG                                        Sample                                                                            Actual                                                                            Pred.                                                                             Error, g/L                                                                           Error, %                                                                             Pred.                                                                             Error, g/L                                                                          Error, %                                  __________________________________________________________________________     4  0.2 -4.7                                                                              -4.9   -2060.0                                                                              -6.0                                                                              -6.2  -2579.3                                    2  0.6 -4.5                                                                              -5.1   -832.2 -3.5                                                                              -4.1  -675.3                                     1  1.4 1.1 -0.3   -21.3  -2.4                                                                              -3.7  -269.4                                    70  5.4 13.5                                                                              8.1    149.7  25.2                                                                              19.8  366.9                                     31  6.1 -1.6                                                                              -7.8   -126.7 0.2 -5.9  -96.1                                     77  7.3 13.4                                                                              6.1    84.3   16.2                                                                              8.9   122.5                                     17  9.2 4.5 -4.7   -50.7  5.1 -4.1  -44.6                                     62  10.0                                                                              23.2                                                                              13.2   131.3  22.2                                                                              12.2  121.4                                     58  13.3                                                                              19.1                                                                              5.8    43.4   24.1                                                                              10.8  80.9                                      41  14.7                                                                              18.6                                                                              3.9    26.4   29.7                                                                              15.0  101.8                                     65  17.8                                                                              26.1                                                                              8.3    46.6   28.1                                                                              10.3  58.0                                      50  19.6                                                                              9.1 -10.5  -53.6  11.9                                                                              -7.7  -39.2                                     83  22.5                                                                              31.0                                                                              8.5    37.8   44.2                                                                              21.7  96.6                                      40  23.4                                                                              25.6                                                                              2.2    9.3    26.7                                                                              3.3   14.3                                      80  24.0                                                                              18.1                                                                              -5.2   -24.5  8.2 -15.8 -65.9                                      7  25.2                                                                              30.6                                                                              5.4    21.2   24.2                                                                              -1.1  -4.2                                      46  26.9                                                                              35.5                                                                              8.6    32.0   36.9                                                                              10.0  37.1                                      74  29.1                                                                              39.0                                                                              9.9    34.0   37.4                                                                              8.3   28.5                                      35  31.2                                                                              43.4                                                                              12.2   39.2   39.6                                                                              8.4   27.0                                      14  32.6                                                                              36.0                                                                              3.4    10.3   36.5                                                                              3.9   11.9                                      32  35.9                                                                              39.4                                                                              3.5    9.7    39.6                                                                              3.7   10.2                                      10  37.3                                                                              28.9                                                                              -8.5   -22.6  30.1                                                                              -7.2  -19.4                                     73  40.8                                                                              29.4                                                                              -11.4  -28.1  19.3                                                                              -21.5 -52.7                                     89  41.8                                                                              52.3                                                                              10.5   25.1   51.4                                                                              9.6   22.8                                      34  42.6                                                                              39.1                                                                              -3.5   -8.2   40.2                                                                              -2.4  -5.6                                      52  45.1                                                                              47.5                                                                              2.4    5.3    47.3                                                                              2.2   4.8                                       29  46.2                                                                              37.9                                                                              -8.3   -17.9  39.8                                                                              -6.4  -13.8                                     68  47.2                                                                              50.7                                                                              3.6    7.5    43.8                                                                              -3.4  -7.2                                      20  52.1                                                                              59.3                                                                              7.2    13.9   60.9                                                                              8.8   16.9                                      61  54.0                                                                              51.5                                                                              -2.6   -4.8   61.2                                                                              7.2   13.3                                      53  55.6                                                                              59.1                                                                              3.6    6.4    58.0                                                                              2.4   4.4                                       16  56.3                                                                              54.1                                                                              -2.2   -3.9   48.1                                                                              -8.1  -14.4                                     23  58.6                                                                              64.5                                                                              5.6    9.6    59.5                                                                              0.6   1.1                                       28  62.2                                                                              59.5                                                                              -2.7   -4.4   52.7                                                                              -9.5  -15.3                                     85  65.4                                                                              48.6                                                                              -16.7  -25.6  63.4                                                                              -1.9  -3.0                                       5  67.0                                                                              92.2                                                                              25.2   37.6   95.4                                                                              28.3  42.3                                      44  68.9                                                                              75.5                                                                              6.6    9.7    73.1                                                                              4.2   6.1                                       13  71.3                                                                              77.6                                                                              6.5    9.1    76.2                                                                              4.9   6.2                                       38  73.9                                                                              61.6                                                                              -12.4  -16.7  63.0                                                                              -10.9 -14.7                                     79  76.9                                                                              75.3                                                                              -1.7   -2.2   78.8                                                                              1.7   2.2                                       19  79.4                                                                              76.4                                                                              -3.0   -3.8   72.1                                                                              -7.3  -9.2                                      43  81.6                                                                              87.2                                                                              5.7    6.9    80.4                                                                              -1.1  -1.4                                      47  83.6                                                                              69.2                                                                              -14.4  -17.3  86.0                                                                              2.4   2.9                                       88  86.8                                                                              85.8                                                                              -1.0   -1.1   85.6                                                                              -1.2  -1.4                                      22  88.5                                                                              77.5                                                                              -11.0  -12.4  72.1                                                                              -16.4 -18.5                                     26  90.8                                                                              90.3                                                                              -0.5   -0.6   93.1                                                                              2.2   2.4                                       49  91.9                                                                              85.5                                                                              -6.4   -6.9   87.4                                                                              -4.5  -4.9                                      64  95.5                                                                              91.6                                                                              -3.8   -4.0   85.7                                                                              -9.8  -10.3                                      8  100.2                                                                             89.6                                                                              -10.4  -10.4  94.7                                                                              -5.6  -5.6                                      59  103.8                                                                             107.2                                                                             3.4    3.3    103.4                                                                             -0.4  -0.4                                      56  107.0                                                                             106.3                                                                             -0.7   -0.7   93.9                                                                              -13.1 -12.3                                     76  109.2                                                                             113.2                                                                             4.7    4.3    108.1                                                                             -1.1  -1.0                                      55  110.7                                                                             97.1                                                                              - 13.6 -12.3  96.2                                                                              -14.6 -13.2                                     11  112.3                                                                             119.8                                                                             7.6    6.8    135.1                                                                             22.8  20.3                                      37  113.5                                                                             109.7                                                                             -3.8   -3.4   104.9                                                                             -8.6  -7.6                                      82  114.0                                                                             99.3                                                                              -15.5  -13.5  88.7                                                                              -26.1 -22.8                                     71  117.5                                                                             122.6                                                                             5.1    4.4    117.1                                                                             -0.4  -0.3                                      __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________            mud density not used                                                                            mud density input                                   POTASSIUM   Model PR01        Model PG                                        Sample                                                                            Actual                                                                            Pred.                                                                             Error, g/L                                                                           Error, %                                                                             Pred.                                                                             Error, g/L                                                                          Error, %                                  __________________________________________________________________________    50  0.1 -0.4                                                                              -0.5   -442.4 -0.4                                                                              -0.5  -385.5                                    11  0.2 5.5 5.2    2254.4 0.1 -0.1  -51.5                                     38  0.4 8.5 8.1    2287.2 -1.8                                                                              -2.2  -607.0                                    34  0.7 -2.5                                                                              -3.2   -475.0 -1.0                                                                              -1.6  -243.5                                    17  0.7 -6.8                                                                              -7.5   -1008.8                                                                              -4.9                                                                              -5.7  -765.2                                    65  0.8 7.0 6.2    804.4  6.0 5.3   678.7                                      4  0.9 -1.8                                                                              -2.7   -291.9 -2.7                                                                              -3.7  -395.3                                    73  1.1 -4.4                                                                              -5.5   -506.2 6.4 5.4   495.6                                      5  1.2 -2.0                                                                              -3.2   -265.8 -7.2                                                                              -8.4  -694.8                                    80  1.3 7.5 6.2    482.7  7.4 6.1   475.0                                     37  1.8 0.5 -1.3   -73.5  3.5 1.7   94.0                                      20  2.0 -0.3                                                                              -2.2   -113.3 -4.6                                                                              -6.6  -332.5                                    49  2.4 11.3                                                                              8.9    370.6  7.2 4.8   201.1                                      2  2.6 6.2 3.6    138.6  0.9 -1.7  -65.3                                     31  2.8 -5.8                                                                              -8.6   -308.5 1.4 -1.4  -48.6                                     82  2.9 6.6 3.7    130.8  19.5                                                                              16.6  581.6                                      8  3.2 -1.7                                                                              -4.9   -152.1 -2.8                                                                              -6.1  -188.0                                    26  3.4 5.1 1.7    48.3   3.0 -0.5  -14.0                                     88  3.7 17.3                                                                              13.6   367.7  21.3                                                                              17.6  473.5                                     13  4.0 -0.5                                                                              -4.5   -113.7 -2.3                                                                              -6.3  -158.2                                    61  7.2 16.5                                                                              9.3    130.1  11.7                                                                              4.5   62.5                                      77  8.0 13.3                                                                              5.4    67.8   13.4                                                                              5.4   68.3                                      14  10.4                                                                              15.5                                                                              5.1    48.7   10.5                                                                              0.1   0.5                                       40  13.7                                                                              16.0                                                                              2.3    16.8   16.8                                                                              3.1   22.4                                       1  14.4                                                                              17.7                                                                              3.4    23.4   22.7                                                                              8.3   57.9                                      79  15.2                                                                              20.1                                                                              4.9    32.3   24.4                                                                              9.2   60.5                                      64  1 6.5                                                                             16.3                                                                              -0.1   -0.9   23.8                                                                              7.3   44.6                                      56  17.3                                                                              13.0                                                                              -4.3   -25.1  24.0                                                                              6.7   38.9                                      58  19.1                                                                              16.0                                                                              -3.2   -16.5  20.9                                                                              1.7   9.1                                       22  20.1                                                                              13.0                                                                              -7.1   -35.4  14.9                                                                              -5.2  -25.7                                     52  21.2                                                                              21.1                                                                              -0.1   -0.7   24.2                                                                              3.0   14.1                                      28  21.9                                                                              14.9                                                                              -7.0   -31.8  17.1                                                                              -4.8  -21.7                                     68  23.4                                                                              19.6                                                                              -3.8   -16.2  26.3                                                                              2.9   12.5                                      74  25.6                                                                              23.4                                                                              -2.2   -8.6   26.4                                                                              0.8   3.1                                       32  26.7                                                                              32.3                                                                              5.7    21.3   30.5                                                                              3.8   14.4                                      23  27.9                                                                              30.2                                                                              2.4    8.5    33.1                                                                              5.2   18.8                                      76  28.7                                                                              24.4                                                                              -4.2   -14.8  35.7                                                                              7.0   24.5                                      83  32.1                                                                              45.4                                                                              13.4   41.7   30.3                                                                              -1.8  -5.5                                      46  34.7                                                                              33.6                                                                              -1.1   -3.1   37.1                                                                              2.4   6.9                                       53  35.7                                                                              39.6                                                                              3.9    10.9   30.6                                                                              -5.1  -14.4                                     19  37.0                                                                              33.2                                                                              -3.9   -10.5  36.9                                                                              -0.2  -0.4                                      35  40.6                                                                              42.8                                                                              2.2    5.4    44.3                                                                              3.7   9.1                                       43  43.8                                                                              38.8                                                                              -5.0   -11.4  44.2                                                                              0.3   0.8                                       59  46.3                                                                              41.2                                                                              -5.1   -11.0  45.9                                                                              -0.4  -1.0                                      71  47.1                                                                              48.4                                                                              1.3    2.8    52.2                                                                              5.1   10.9                                      10  47.9                                                                              47.9                                                                              0.1    0.2    54.0                                                                              6.2   12.9                                      44  50.0                                                                              53.6                                                                              3.5    7.0    48.8                                                                              -1.3  -2.6                                      62  53.4                                                                              51.4                                                                              -1.9   -3.6   49.2                                                                              -4.1  -7.8                                      41  59.9                                                                              58.9                                                                              -1.0   -1.7   46.7                                                                              -13.1 -21.9                                     89  64.4                                                                              57.8                                                                              -6.5   -10.2  52.3                                                                              -12.1 -18.8                                     70  70.4                                                                              58.6                                                                              -11.9  -16.8  50.2                                                                              -20.2 -28.7                                     55  74.5                                                                              70.4                                                                              -4.1   -5.5   67.0                                                                              -7.5  -10.1                                      7  84.1                                                                              98.1                                                                              14.0   16.6   110.9                                                                             26.8  31.9                                      29  91.0                                                                              91.2                                                                              0.2    0.3    83.3                                                                              -7.7  -8.4                                      47  95.8                                                                              96.8                                                                              2.9    3.1    81.1                                                                              -14.7 -15.4                                     16  99.9                                                                              101.7                                                                             1.6    1.8    111.7                                                                             11.9  11.8                                      85  103.6                                                                             81.7                                                                              -21.9  -21.2  63.9                                                                              -39.8 -38.4                                     __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________            mud density not used                                                                          mud density input                                     CHLORIDE    Model P2        Model PG                                          Sample                                                                            Actual                                                                            Pred.                                                                             Error, g/L                                                                          Error, %                                                                            Pred.                                                                             Error, g/L                                                                          Error, %                                    __________________________________________________________________________    80  5.3 23.1                                                                              17.8  337.9 16.1                                                                              10.9  205.8                                        5  6.0 -5.3                                                                              -11.3 -187.5                                                                              -12.0                                                                             -18.0 -298.9                                      49  6.6 17.5                                                                              10.9  164.5 17.4                                                                              10.8  163.2                                       31  6.9 -7.6                                                                              -14.5 -209.9                                                                              5.6 -1.3  -18.3                                       73  7.4 12.8                                                                              5.4   72.5  14.6                                                                              7.2   96.7                                        82  7.8 23.5                                                                              15.7  200.0 34.5                                                                              26.7  341.2                                       17  9.1 -1.9                                                                              -11.0 -121.0                                                                              3.7 -5.4  -59.3                                        2  9.9 15.6                                                                              5.7   57.4  8.0 -1.9  -19.2                                       11  10.5                                                                              -7.1                                                                              -17.6 -167.0                                                                              -4.1                                                                              -14.6 -138.5                                      50  11.8                                                                              19.9                                                                              8.1   69.2  14.8                                                                              3.0   25.5                                        20  17.3                                                                              17.7                                                                              0.4   2.5   10.7                                                                              -6.5  -37.8                                        4  18.9                                                                              23.3                                                                              4.4   23.2  22.2                                                                              3.3   17.6                                        40  22.0                                                                              25.1                                                                              3.1   13.8  28.9                                                                              6.8   31.0                                        26  26.8                                                                              25.2                                                                              -1.7                                                              31 6.2                                                                            25.0                                                                              -1.8                                                                              -6.7                                                              14  29.3                                                                              36.9                                                                              7.6   25.9  28.6                                                                              -0.7  -2.4                                        52  37.7                                                                              43.7                                                                              6.0   15.9  48.5                                                                              10.8  28.8                                        13  41.0                                                                              44.0                                                                              3.0   7.3   38.6                                                                              -2.4  -5.8                                        32  43.5                                                                              60.6                                                                              17.1  39.2  50.0                                                                              6.5   14.9                                         1  45.6                                                                              47.7                                                                              2.1   4.6   57.6                                                                              12.0  26.3                                        68  46.9                                                                              52.5                                                                              5.6   11.9  54.8                                                                              7.9   16.9                                        37  48.3                                                                              43.9                                                                              -4.4  -9.1  54.2                                                                              5.9   12.2                                        56  51.1                                                                              59.1                                                                              8.0   15.7  63.1                                                                              12.0  23.5                                        23  54.2                                                                              55.8                                                                              1.6   3.0   58.1                                                                              4.0   7.4                                         64  55.8                                                                              59.1                                                                              3.3   5.9   68.9                                                                              13.1  23.4                                        46  58.9                                                                              61.4                                                                              2.5   4.3   68.5                                                                              9.6   16.3                                        71  60.3                                                                              73.9                                                                              13.5  22.4  86.6                                                                              26.3  43.6                                        62  62.9                                                                              68.4                                                                              5.6   8.9   68.2                                                                              5.3   8.5                                          8  65.5                                                                              65.2                                                                              -0.3  -0.5  64.8                                                                              -0.8  -1.2                                        35  66.8                                                                              78.7                                                                              11.9  17.2  75.7                                                                              9.0   13.5                                        43  75.0                                                                              79.5                                                                              4.5   6.0   83.9                                                                              8.9   11.9                                         7  80.0                                                                              82.3                                                                              2.3   2.9   95.3                                                                              15.3  19.1                                        44  83.6                                                                              104.6                                                                             21.0  25.1  90.7                                                                              7.2   8.6                                         89  86.1                                                                              95.3                                                                              9.2   10.6  88.0                                                                              1.9   2.2                                         19  87.8                                                                              88.8                                                                              1.0   1.2   88.7                                                                              0.9   1.0                                         59  89.4                                                                              89.0                                                                              -0.4  -0.4  98.9                                                                              9.6   10.7                                        38  90.8                                                                              112.8                                                                             22.0  24.3  93.3                                                                              2.5   2.7                                         74  94.7                                                                              85.1                                                                              -9.6  -10.2 89.6                                                                              -5.2  -5.5                                        16  98.0                                                                              101.2                                                                             3.2   3.3   109.1                                                                             11.1  11.3                                        10  99.2                                                                              102.8                                                                             3.6   3.6   112.4                                                                             13.2  13.3                                        55  100.0                                                                             111.7                                                                             11.7  11.7  108.2                                                                             8.2   8.2                                         47  100.6                                                                             47.6                                                                              -53.0 -52.6 33.7                                                                              -66.9 -66.5                                       77  102.4                                                                             91.7                                                                              -10.7 -10.4 90.9                                                                              -11.4 -11.2                                       58  104.3                                                                             93.5                                                                              -10.8 -10.4 103.3                                                                             -1.0  -0.9                                        88  105.9                                                                             95.0                                                                              -10.9 -10.3 101.8                                                                             -4.1  -3.8                                        76  107.6                                                                             103.0                                                                             -4.6  -4.3  112.2                                                                             4.6   4.3                                         85  112.6                                                                             105.9                                                                             -6.7  -6.0  90.1                                                                              -22.5 -20.0                                       79  118.8                                                                             108.9                                                                             -9.9  -8.4  110.9                                                                             -8.0  -6.7                                        70  120.9                                                                             114.3                                                                             -6.6  -5.5  111.9                                                                             -9.0  -7.4                                        83  123.7                                                                             119.6                                                                             -4.1  -3.3  110.5                                                                             -13.2 -10.7                                       53  126.2                                                                             138.6                                                                             11.7  9.3   119.1                                                                             -7.8  -6.1                                        29  130.0                                                                             139.8                                                                             9.8   7.5   130.3                                                                             0.3   0.3                                         41  133.7                                                                             99.0                                                                              -34.7 -26.0 89.2                                                                              -44.5 -33.3                                       22  133.8                                                                             135.3                                                                             1.5   1.1   130.9                                                                             -2.9  -2.2                                        65  135.1                                                                             121.3                                                                             -13.9 -10.3 123.7                                                                             -11.5 -8.5                                        61  138.4                                                                             123.0                                                                             -15.4 -11.2 126.7                                                                             -11.7 -8.5                                        28  143.5                                                                             143.7                                                                             0.1   0.1   142.4                                                                             -1.1  -0.8                                        34  150.7                                                                             139.0                                                                             -11.7 -7.7  147.2                                                                             -3.5  -2.3                                        __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________            mud density not used                                                                         mud density input                                      LGS         Model P2       Model PG                                           Sample                                                                            Actual                                                                            Pred.                                                                             Error, g/L                                                                          Error, %                                                                           Pred.                                                                             Error, g/L                                                                          Error, %                                     __________________________________________________________________________     2  21.31                                                                             31.14                                                                             9.83  46.10                                                                              22.77                                                                             1.46  6.85                                          4  25.83                                                                             41.98                                                                             16.14 62.48                                                                              31.44                                                                             5.60  21.68                                         7  59.03                                                                             81.78                                                                             22.75 38.53                                                                              63.47                                                                             4.44  7.52                                          1  63.23                                                                             44.29                                                                             -18.95                                                                              -29.96                                                                             34.19                                                                             -29.04                                                                              -45.93                                       17  72.63                                                                             31.31                                                                             -41.32                                                                              -56.89                                                                             93.81                                                                             21.18 29.15                                        10  117.74                                                                            132.49                                                                            14.73 12.51                                                                              117.26                                                                            -0.50 -0.42                                         5  120.50                                                                            191.09                                                                            70.51 58.48                                                                              141.68                                                                            21.10 17.50                                        14  126.35                                                                            100.12                                                                            -26.23                                                                              -20.76                                                                             121.64                                                                            -4.71 -3.73                                        16  138.37                                                                            161.25                                                                            22.88 16.54                                                                              154.15                                                                            15.78 11.40                                        31  145.24                                                                            112.22                                                                            -33.02                                                                              -22.73                                                                             174.77                                                                            29.53 20.33                                        20  155.96                                                                            175.75                                                                            19.79 12.69                                                                              175.21                                                                            19.25 12.34                                        13  178.87                                                                            207.46                                                                            28.59 15.98                                                                              182.39                                                                            3.52  1.97                                         11  205.68                                                                            207.31                                                                            1.63  0.79 226.76                                                                            21.08 10.25                                        29  213.68                                                                            219.70                                                                            6.02  2.82 224.15                                                                            10.47 4.90                                          8  218.33                                                                            217.39                                                                            -0.94 - 0.43                                                                             206.98                                                                            -11.35                                                                              -5.20                                        23  244.94                                                                            177.08                                                                            -67.86                                                                              -27.70                                                                             213.48                                                                            -31.46                                                                              -12.84                                       26  253.43                                                                            228.05                                                                            -25.38                                                                              -10.01                                                                             267.74                                                                            14.31 5.65                                         40  256.81                                                                            258.79                                                                            1.98  0.77 270.94                                                                            14.13 5.50                                         32  258.82                                                                            257.71                                                                            -1.11 -0.43                                                                              249.17                                                                            -9.65 -3.73                                        41  265.77                                                                            290.50                                                                            24.73 9.31 311.92                                                                            46.15 17.36                                        28  282.75                                                                            317.50                                                                            34.75 12.29                                                                              290.77                                                                            8.02  2.84                                         50  288.08                                                                            349.69                                                                            61.61 21.39                                                                              306.25                                                                            18.17 6.31                                         19  293.95                                                                            230.19                                                                            -63.76                                                                              -21.69                                                                             236.92                                                                            -57.03                                                                              -19.40                                       35  307.11                                                                            258.11                                                                            -49.00                                                                              -15.96                                                                             278.13                                                                            -28.98                                                                              -9.44                                        34  313.00                                                                            337.89                                                                            24.89 7.95 325.36                                                                            12.36 3.95                                         22  325.59                                                                            296.61                                                                            -28.98                                                                              -8.90                                                                              289.92                                                                            -35.67                                                                              -10.96                                       38  342.20                                                                            376.25                                                                            34.05 9.95 342.46                                                                            0.26  0.08                                         46  365.56                                                                            331.69                                                                            -33.87                                                                              -9.27                                                                              352.75                                                                            -12.81                                                                              -3.50                                        47  368.73                                                                            414.84                                                                            46.11 12.51                                                                              403.53                                                                            34.80 9.44                                         37  370.84                                                                            370.63                                                                            -0.21 -0.06                                                                              383.34                                                                            12.50 3.37                                         49  388.62                                                                            421.14                                                                            32.52 8.37 406.91                                                                            18.29 4.71                                         52  394.03                                                                            386.06                                                                            -7.97 -2.02                                                                              393.50                                                                            -0.53 -0.13                                        53  419.82                                                                            465.09                                                                            45.27 10.78                                                                              456.05                                                                            36.23 8.63                                         58  437.60                                                                            455.34                                                                            17.74 4.05 436.90                                                                            -0.70 -0.16                                        43  447.97                                                                            395.26                                                                            -52.71                                                                              -11.77                                                                             410.79                                                                            -37.18                                                                              -8.30                                        44  454.15                                                                            402.81                                                                            -51.34                                                                              -11.30                                                                             412.92                                                                            -41.23                                                                              -9.08                                        70  475.38                                                                            522.57                                                                            47.19 9.93 529.73                                                                            54.35 11.43                                        55  481.36                                                                            522.43                                                                            41.07 8.53 516.94                                                                            35.58 7.39                                         62  494.99                                                                            494.39                                                                            -0.60 -0.12                                                                              422.66                                                                            -72.33                                                                              -14.61                                       65  497.06                                                                            548.40                                                                            51.34 10.33                                                                              511.79                                                                            14.73 2.96                                         56  525.89                                                                            567.63                                                                            41.74 7.94 517.72                                                                            -8.17 -1.55                                        73  527.77                                                                            566.28                                                                            38.51 7.30 496.06                                                                            -31.71                                                                              -6.01                                        61  528.68                                                                            501.39                                                                            -27.27                                                                              -5.16                                                                              548.75                                                                            20.09 3.80                                         68  549.56                                                                            558.26                                                                            8.70  1.58 521.52                                                                            -28.04                                                                              -5.10                                        80  574.27                                                                            559.99                                                                            -14.28                                                                              -2.49                                                                              543.44                                                                            -30.83                                                                              -5.37                                        64  578.54                                                                            559.91                                                                            -18.63                                                                              -3.22                                                                              572.56                                                                            -5.98 -1.03                                        77  593.69                                                                            587.01                                                                            -6.68 -1.13                                                                              583.59                                                                            -10.10                                                                              -1.70                                        59  614.65                                                                            544.73                                                                            -69.92                                                                              -11.38                                                                             586.03                                                                            -28.62                                                                              -4.66                                        74  618.22                                                                            615.54                                                                            -2.68 -0.43                                                                              587.28                                                                            -30.94                                                                              -5.00                                        83  660.96                                                                            643.20                                                                            -17.76                                                                              -2.69                                                                              702.05                                                                            41.09 6.22                                         85  698.73                                                                            743.44                                                                            44.71 6.40 720.25                                                                            21.52 3.08                                         71  728.90                                                                            670.93                                                                            -57.97                                                                              -7.95                                                                              701.69                                                                            -27.21                                                                              -3.73                                        82  732.61                                                                            737.75                                                                            5.14  0.70 715.27                                                                            -17.34                                                                              -2.37                                        89  732.73                                                                            719.08                                                                            -13.65                                                                              -1.86                                                                              765.17                                                                            32.44 4.43                                         79  741.00                                                                            717.82                                                                            -23.18                                                                              -3.13                                                                              741.63                                                                            0.63  0.09                                         76  770.58                                                                            747.66                                                                            -22.92                                                                              -2.97                                                                              772.15                                                                            1.57  0.20                                         88  842.56                                                                            805.83                                                                            -36.73                                                                              -4.36                                                                              848.06                                                                            5.50  0.65                                         __________________________________________________________________________

                  TABLE 8                                                         ______________________________________                                                 mud density not used                                                                          mud density input                                    WATER    Model P2        Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        85   472.8   499.8   27.3  5.8   527.8 55.3  11.7                             88   474.1   506.7   32.7  6.9   481.4 7.4   1.6                              89   528.0   523.7   -4.3  -0.8  509.1 -18.9 -3.6                             76   532.2   535.9   3.7   0.7   519.6 -12.5 -2.4                             79   548.1   550.7   2.7   0.5   539.9 -8.2  -1.5                             71   559.8   580.7   20.9  3.7   558.4 -1.4  -0.2                             83   583.6   574.2   -9.4  -1.6  556.9 -26.7 -4.6                             82   584.1   574.7   -9.4  -1.6  573.2 -10.8 -1.9                             74   611.6   622.4   10.8  1.8   629.7 18.2  3.0                              59   623.3   649.1   25.9  4.1   624.1 0.9   0.1                              62   645.8   684.4   38.5  6.0   716.5 70.7  11.0                             77   646.0   636.8   -9.3  -1.4  636.6 -9.4  -1.5                             55   651.5   634.1   -17.5 -2.7  644.0 -7.5  -1.2                             64   659.3   662.8   3.5   0.5   648.6 -10.7 -1.6                             61   664.3   679.7   15.4  2.3   655.8 -8.5  -1.3                             70   669.2   643.7   -25.5 -3.8  644.0 -25.2 -3.8                             68   672.2   662.7   -9.5  -1.4  676.3 4.0   0.6                              80   676.7   668.4   -8.3  -1.2  677.7 1.1   0.2                              65   684.3   664.6   -19.7 -2.9  678.3 -6.0  -0.9                             56   684.6   659.7   -24.8 -3.6  680.9 -3.7  -0.5                             73   700.6   680.9   -19.7 -2.8  706.5 5.9   0.8                              44   707.6   706.8   -0.8  -0.1  719.9 12.3  1.7                              53   707.9   670.4   -37.4 -5.3  697.3 -10.5 -1.5                             47   707.9   697.3   -10.6 -1.5  720.8 12.9  1.8                              43   714.1   734.6   20.4  2.9   724.8 10.6  1.5                              58   728.0   720.4   -7.6  -1.0  717.9 -10.0 -1.4                             38   741.6   748.0   6.4   0.9   784.6 43.0  5.8                              29   746.0   781.2   35.2  4.7   787.7 41.6  5.6                              52   768.5   763.6   -4.9  -0.6  755.0 -13.5 -1.8                             49   772.3   756.9   -15.5 -2.0  764.0 -8.3  -1.1                             37   773.0   784.9   11.9  1.5   768.6 -4.4  -0.6                             22   774.9   784.9   10.0  1.3   792.1 17.3  2.2                              46   776.4   783.4   7.0   0.9   766.4 -10.0 -1.3                             41   787.4   777.4   -10.1 -1.3  779.2 - 8.3 -1.1                             34   789.6   785.8   -3.8  -0.5  782.2 -7.5  -0.9                             28   794.4   776.5   -17.9 -2.3  789.1 -5.3  -0.7                             19   796.5   823.0   26.5  3.3   819.2 22.7  2.9                              35   799.9   807.1   7.2   0.9   801.4 1.6   0.2                              50   830.9   803.6   -27.3 -3.3  826.3 -4.6  -0.6                             32   832.7   816.8   -15.9 -1.9  831.9 -0.8  -0.1                             16   841.3   820.7   -20.6 -2.5  812.4 -28.9 -3.4                             26   842.0   857.7   15.7  1.9   838.5 -3.5  -0.4                             23   842.6   864.8   22.2  2.6   844.6 2.0   0.2                              40   851.2   845.6   -5.6  -0.7  835.0 -16.2 -1.9                             8    852.5   857.4   4.9   0.6   860.5 8.0   0.9                              11   874.6   877.7   3.2   0.4   863.7 -10.9 -1.2                             13   882.3   868.5   -13.8 -1.6  884.0 1.7   0.2                              10   885.1   874.4   -10.7 -1.2  868.1 -17.1 -1.9                             7    897.7   876.6   -21.0 -2.3  867.5 -30.1 -3.4                             20   897.7   893.7   -4.0  -0.4  899.7 2.0   0.2                              31   911.4   951.0   39.6  4.3   905.7 -5.6  -0.6                             14   915.9   919.8   3.9   0.4   917.9 2.0   0.2                              5    926.4   892.3   -34.1 -3.7  920.8 -5.6  - 0.6                            1    954.4   961.0   6.5   0.7   956.2 1.7   0.2                              17   959.5   990.1   30.6  3.2   954.9 -4.6  -0.5                             2    979.7   976.4   -3.3  -0.3  992.8 13.1  1.3                              4    986.9   976.5   -10.4 -1.1  986.0 -0.9  -0.1                             ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                                 mud density not used                                                                          mud density input                                    Z        Model P1        Model PE                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        2    7.49    7.79    0.30  3.95  8.08  0.58  7.77                             4    7.70    7.97    0.27  3.54  8.29  0.59  7.69                             1    7.96    7.88    -0.07 -0.93 8.51  0.58  7.00                             5    8.48    8.31    -0.16 -1.93 9.02  0.55  6.45                             8    9.66    9.14    -0.52 -5.37 10.07 0.41  4.21                             7    9.71    9.73    0.02  0.19  9.39  -0.32 -3.31                            11   9.84    9.52    -0.32 -3.26 10.15 0.31  3.13                             10   10.06   9.90    -0.15 -1.53 9.92  -0.14 -1.35                            14   10.13   10.24   0.11  1.07  10.21 0.07  0.72                             13   10.30   10.46   0.16  1.60  10.44 0.15  1.41                             17   10.30   10.27   -0.03 -0.32 10.20 -0.10 -0.99                            20   11.36   11.45   0.09  0.79  11.19 -0.16 -1.44                            16   11.79   12.20   0.41  3.47  11.23 -0.57 -4.80                            19   11.86   11.91   0.05  0.44  11.92 0.06  0.53                             23   12.40   12.55   0.15  1.20  12.31 -0.09 -0.74                            22   12.73   12.72   -0.02 -0.14 12.72 -0.01 -0.10                            26   13.12   13.42   0.30  2.25  13.00 -0.13 -0.96                            28   14.28   14.01   -0.27 -1.89 13.81 -0.47 -3.27                            31   14.41   14.48   0.06  0.45  13.86 -0.56 -3.85                            32   14.94   15.03   0.10  0.64  14.79 -0.15 -0.99                            29   15.08   15.29   0.21  1.39  14.00 -1.08 -7.16                            35   15.75   15.86   0.12  0.75  15.65 -0.10 -0.61                            34   15.81   15.63   -0.18 -1.13 15.35 -0.46 -2.92                            37   16.20   15.92   -0.29 -1.79 15.90 -0.30 -1.88                            38   16.77   16.82   0.05  0.31  16.47 -0.30 -1.77                            40   16.95   16.82   -0.14 -0.80 16.54 -0.41 -2.42                            41   17.70   17.28   -0.42 -2.35 17.18 -0.52 -2.94                            43   17.70   17.71   0.02  0.09  17.90 0.20  1.14                             44   18.04   18.12   0.07  0.40  18.28 0.24  1.32                             46   18.62   18.56   -0.06 -0.30 18.67 0.06  0.31                             49   18.90   18.65   -0.25 -1.30 18.73 -0.17 -0.89                            47   19.11   18.78   -0.32 -1.70 18.87 -0.24 -1.25                            50   19.46   19.81   0.35  1.80  19.46 0.00  0.02                             52   19.76   19.64   -0.12 -0.60 19.97 0.21  1.04                             53   20.17   20.25   0.08  0.40  20.21 0.04  0.21                             56   20.59   21.08   0.48  2.34  21.28 0.68  3.32                             55   20.67   20.74   0.07  0.34  20.72 0.05  0.25                             59   21.02   21.09   0.07  0.33  21.45 0.43  2.05                             58   21.38   21.43   0.05  0.25  21.70 0.33  1.54                             61   21.90   21.77   -0.13 -0.61 22.04 0.13  0.60                             64   22.37   22.58   0.21  0.94  22.94 0.57  2.55                             62   22.68   22.36   -0.31 -1.39 22.35 -0.33 -1.44                            65   23.04   22.88   -0.16 -0.68 23.06 0.02  0.09                             71   23.58   23.48   -0.10 -0.44 23.77 0.18  0.77                             68   23.61   23.78   0.17  0.71  24.07 0.47  1.97                             70   24.47   24.32   -0.15 -0.61 24.35 -0.12 -0.48                            76   24.64   24.88   0.23  0.95  25.16 0.51  2.09                             73   25.00   25.09   0.10  0.38  25.46 0.47  1.87                             74   25.01   25.05   0.04  0.17  25.19 0.18  0.71                             79   25.55   25.83   0.28  1.10  25.97 0.42  1.65                             77   25.75   25.80   0.05  0.21  25.95 0.20  0.78                             82   26.16   26.38   0.22  0.84  26.50 0.34  1.30                             80   26.62   26.63   0.01  0.03  26.47 -0.15 -0.55                            83   26.86   26.20   -0.66 -2.47 26.39 -0.46 -1.73                            85   27.56   27.53   -0.03 -0.11 27.00 -0.57 -2.06                            88   27.68   27.69   0.01  0.03  27.21 -0.47 - 1.69                           89   28.36   28.23   -0.14 -0.49 27.63 -0.74 -2.60                            ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                        SG                                                                                       Model P2                                                           Sample   Actual  Pred.      Error, g/L                                                                            Error, %                                  ______________________________________                                        2        1.02    1.05       0.03    2.71                                      4        1.04    1.05       0.01    1.16                                      1        1.08    1.06       -0.02   -1.66                                     17       1.11    1.04       -0.07   -6.36                                     5        1.13    1.20       0.07    6.09                                      7        1.16    1.19       0.03    2.17                                      14       1.16    1.14       -0.02   -2.00                                     20       1.21    1.22       0.02    1.41                                      10       1.21    1.21       0.00    0.06                                      13       1.22    1.25       0.03    2.53                                      11       1.24    1.24       0.00    0.15                                      31       1.24    1.19       -0.06   -4.47                                     8        1.26    1.27       0.01    0.73                                      16       1.29    1.31       0.01    1.04                                      23       1.33    1.26       -0.06   -4.77                                     26       1.34    1.31       -0.03   -2.33                                     19       1.37    1.33       -0.04   -2.62                                     29       1.38    1.42       0.04    2.74                                      32       1.38    1.41       0.03    1.97                                      40       1.42    1.41       -0.01   -0.90                                     22       1.44    1.42       -0.02   -1.31                                     28       1.45    1.46       0.01    0.68                                      35       1.45    1.43       -0.02   -1.67                                     38       1.48    1.57       0.09    5.80                                      50       1.50    1.57       0.07    4.59                                      34       1.50    1.49       -0.01   -0.79                                     41       1.53    1.50       -0.02   -1.44                                     37       1.54    1.51       -0.02   -1.55                                     46       1.58    1.56       -0.03   - 1.72                                    49       1.60    1.62       0.02    1.46                                      52       1.64    1.63       -0.01   -0.45                                     43       1.65    1.61       -0.03   -2.08                                     44       1.66    1.65       -0.01   -0.88                                     47       1.68    1.67       -0.02   -0.93                                     53       1.73    1.78       0.05    2.67                                      58       1.75    1.77       0.02    1.07                                      62       1.76    1.84       0.09    4.53                                      56       1.81    1.86       0.05    2.90                                      55       1.83    1.86       0.03    1.53                                      65       1.87    1.91       0.04    2.14                                      61       1.88    1.84       -0.04   -2.22                                     68       1.92    1.94       0.02    1.28                                      73       1.93    1.99       0.06    3.17                                      64       1.93    1.90       -0.03   -1.48                                     59       1.94    1.86       -0.08   -4.35                                     70       1.95    1.97       0.02    1.19                                      80       2.03    2.03       0.00    0.02                                      74       2.04    2.06       0.01    0.61                                      77       2.07    2.06       -0.01   -0.28                                     71       2.13    2.06       -0.07   -3.28                                     82       2.22    2.22       0.00    0.00                                      83       2.22    2.18       -0.04   -1.90                                     79       2.24    2.22       -0.02   -0.95                                     76       2.24    2.22       -0.03   -1.13                                     85       2.28    2.34       0.05    2.25                                      89       2.38    2.33       -0.04   -1.79                                     88       2.41    2.38       -0.03   -1.30                                     ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    BARITE   Model PA        Model PE                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        9    38.3    30.9    -7.4  -19.3 32.8  -5.5  -14.3                            12   67.3    64.1    -3.2  -4.8  78.9  11.6  17.3                             18   119.5   120.5   1.0   0.8   131.4 11.9  10.0                             21   154.4   156.4   2.0   1.3   157.1 2.7   1.7                              24   183.7   177.3   -6.5  -3.5  185.2 1.4   0.8                              27   226.6   234.7   8.1   3.6   231.1 4.4   2.0                              30   273.2   257.5   -15.8 -5.8  264.4 -8.9  -3.2                             33   323.8   341.5   17.7  5.5   330.7 6.8   2.1                              36   373.8   380.6   6.8   1.8   347.3 -26.5 -7.1                             39   424.8   446.6   21.8  5.1   443.6 18.8  4.4                              42   467.0   472.5   5.5   1.2   469.8 2.8   0.6                              48   559.2   557.9   -1.4  -0.2  563.3 4.1   0.7                              51   615.5   647.7   32.1  5.2   629.2 13.7  2.2                              54   678.5   681.3   2.8   0.4   694.3 15.8  2.3                              57   741.0   759.6   18.7  2.5   759.8 18.8  2.5                              60   797.0   783.1   -13.9 -1.7  776.5 - 20.6                                                                              -2.6                             63   867.7   883.3   15.6  1.8   876.7 9.0   1.0                              66   930.1   943.9   13.8  1.5   925.5 -4.6  -0.5                             69   1000.9  1035.7  34.8  3.5   1016.5                                                                              15.6  1.6                              72   1076.9  1083.9  7.0   0.6   1070.5                                                                              -6.4  -0.6                             75   1152.5  1188.6  36.1  3.1   1165.3                                                                              12.8  1.1                              78   1231.1  1257.2  26.1  2.1   1230.0                                                                              -1.1  -0.1                             81   1298.0  1300.0  2.0   0.2   1315.1                                                                              17.1  1.3                              84   1385.5  1336.9  -48.6 -3.5  1389.7                                                                              4.2   0.3                              87   1495.1  1449.2  -45.9 -3.1  1513.0                                                                              17.9  1.2                              ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    CALCIUM  Model PR01      Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        39   3.0     5.1     2.1   69.4  8.0   4.9   162.6                            24   3.2     -13.5   -16.7 -526.1                                                                              6.5   3.4   106.7                            81   3.3     14.8    11.5  345.0 20.6  17.2  518.1                            9    6.9     9.1     2.1   30.9  6.4   -0.5  -7.2                             30   8.2     -5.1    -13.3 -162.8                                                                              7.3   -0.9  -10.9                            48   11.8    26.6    14.8  125.2 30.3  18.4  155.9                            36   17.0    16.6    -0.4  -2.2  16.3  -0.7  -4.0                             69   30.5    32.8    2.3   7.5   22.6  -7.9  -26.0                            66   34.1    36.6    2.5   7.3   23.6  -10.5 -30.8                            78   38.6    42.9    4.3   11.1  21.9  -16.7 -43.3                            42   39.4    34.3    -5.0  -12.8 35.7  -3.6  -9.2                             21   43.7    21.9    -21.8 -49.8 32.6  -11.1 -25.4                            12   49.4    26.2    -23.2 -47.0 39.6  -9.8  -19.8                            51   50.7    57.9    7.2   14.2  45.5  -5.2  - 10.3                           87   51.4    56.2    4.8   9.4   65.6  14.2  27.6                             84   60.8    67.0    6.2   10.2  81.5  20.7  34.0                             60   63.9    62.0    -1.9  -3.0  55.9  -8.0  -12.5                            75   70.5    71.8    1.2   1.8   69.1  -1.4  -2.0                             57   75.0    76.4    1.5   2.0   70.8  -4.1  -5.5                             72   82.5    90.9    8.4   10.1  85.3  2.8   3.4                              33   85.7    79.3    -6.5  -7.5  72.3  -13.4 -15.6                            18   94.3    63.6    -30.7 -32.6 80.8  -13.5 -14.3                            54   97.2    92.4    -4.8  -4.9  90.6  -6.6  -6.8                             27   99.4    75.4    -24.0 -24.1 78.7  -20.7 -20.8                            63   101.7   97.4    -4.3  -4.3  97.5  -4.2  -4.2                             ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        POTAS-   mud density not used                                                                          mud density input                                    SIUM     Model PR01      Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        51   1.0     4.4     3.3   333.9 2.0   1.0   100.5                            42   1.4     3.5     2.1   154.7 0.6   -0.8  -56.9                            9    1.5     -1.1    -2.6  -172.1                                                                              -4.3  -5.8  -384.5                           66   1.6     3.4     1.8   110.3 4.8   3.2   197.4                            69   2.3     5.3     3.0   131.0 6.7   4.4   192.9                            36   3.0     -5.1    -8.2  -269.1                                                                              1.2   -1.8  -59.7                            57   4.1     10.5    6.4   154.7 9.0   4.9   118.5                            60   4.4     4.5     0.1   1.7   9.6   5.2   118.2                            78   4.8     -0.5    -5.3  -110.5                                                                              11.3  6.5   136.1                            21   5.3     1.4     -3.9  -74.4 0.0   -5.3  -100.7                           30   8.8     2.6     -6.2  -70.5 8.1   -0.7  -8.0                             81   9.8     15.4    5.6   57.2  15.9  6.1   62.9                             54   11.0    13.2    2.3   20.6  14.9  4.0   36.0                             18   18.1    17.7    -0.4  -2.0  13.6  -4.5  -24.8                            39   22.6    22.5    -0.1  -0.7  24.2  1.5   6.8                              12   24.9    16.9    -8.0  -32.1 20.9  -3.9  -15.9                            33   30.6    26.4    -4.2  -13.6 25.8  -4.8  -15.6                            24   33.3    36.8    3.5   10.6  39.4  6.1   18.4                             75   38.3    41.6    3.4   8.8   34.9  -3.3  -8.7                             87   39.6    32.7    -6.9  -17.5 40.7  1.1   2.8                              48   56.0    58.0    2.0   3.6   56.0  0.0   0.1                              84   58.0    53.9    -4.1  -7.1  53.1  -4.9  -8.5                             27   77.8    77.8    0.0   -0.1  80.8  3.0   3.9                              72   88.0    72.1    -15.9 -18.1 69.0  -19.0 -21.6                            63   93.1    70.1    -23.0 -24.7 67.1  -26.0 -27.9                            ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    CHLORIDE Model P2        Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        9    2.5     -1.6    -4.1  -162.7                                                                              -6.5  -9.0  -361.3                           51   3.2     15.6    12.4  395.0 9.7   6.5   206.3                            42   4.4     9.1     4.7   106.3 7.6   3.2   71.6                             60   8.2     14.9    6.7   81.3  21.4  13.1  159.4                            78   8.7     19.3    10.6  122.2 19.6  10.9  125.6                            66   15.6    28.2    12.6  80.4  23.3  7.6   48.9                             69   49.9    54.0    4.1   8.2   50.5  0.6   1.2                              39   61.0    61.3    0.3   0.5   66.9  5.9   9.6                              48   70.1    81.2    11.1  15.8  78.2  8.1   11.5                             24   74.0    73.5    -0.5  -0.6  86.5  12.5  16.9                             84   76.6    86.2    9.6   12.6  92.1  15.5  20.3                             30   78.3    74.0    -4.2  -5.4  88.2  9.9   12.7                             36   80.0    76.3    -3.6  -4.5  86.4  6.5   8.1                              87   85.2    81.5    -3.7  -4.4  90.1  4.9   5.7                              27   92.6    96.4    3.8   4.1   101.2 8.6   9.3                              18   109.0   106.6   -2.4  -2.2  106.4 -2.6  - 2.4                            57   111.0   109.3   -1.6  -1.5  105.8 -5.2  -4.7                             72   111.8   116.6   4.8   4.3   111.9 0.1   0.1                              75   114.5   113.3   -1.2  -1.0  105.8 -8.8  -7.7                             12   117.3   105.1   -12.2 -10.4 114.8 -2.5  -2.1                             33   130.9   130.6   -0.4  -0.3  126.1 -4.8  -3.7                             63   136.1   126.3   -9.8  -7.2  125.9 -10.3 -7.5                             54   141.9   128.8   -13.0 -9.2  131.5 -10.4 -7.3                             21   144.2   143.4   -0.8  -0.5  143.7 -0.4  -0.3                             81   148.8   104.4   -44.4 -29.8 105.5 -43.2 -29.1                            ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    LGS      Model P2        Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        9    37.7    25.3    -12.4 -32.9 52.8  15.1  40.2                             24   188.6   103.4   -85.2 -45.2 157.9 -30.7 -16.3                            30   196.8   152.5   -44.4 -22.5 209.6 12.7  -6.5                             12   224.6   128.5   -96.1 -42.8 169.8 -54.7 -24.4                            21   238.3   210.1   -28.1 -11.8 220.9 -17.4 -7.3                             36   243.4   258.7   15.3  6.3   266.9 23.5  9.7                              39   262.3   252.9   -9.4  -3.6  266.2 3.9   1.5                              42   263.7   282.0   18.3  6.9   293.5 29.8  11.3                             27   263.8   225.2   -38.6 -14.6 276.1 12.3  4.7                              18   297.1   211.3   -85.8 -28.9 259.6 -37.5 -12.6                            33   336.0   361.5   25.5  7.6   351.0 15.0  4.5                              51   340.4   418.3   77.9  22.9  363.9 23.5  6.9                              48   389.6   339.4   -50.1 -12.9 349.5 -40.1 -10.3                            60   443.5   470.6   27.0  6.1   448.2 4.7   1.1                              66   454.1   502.3   48.2  10.6  446.7 -7.4  -1.6                             69   501.1   537.6   36.5  7.3   494.0 -7.0  -1.4                             57   503.2   534.0   30.8  6.1   517.6 14.5  2.9                              54   541.6   535.7   -5.9  -1.1  546.7 5.0   0.9                              63   550.4   603.8   53.3  9.7   605.4 55.0  10.0                             78   585.2   613.3   28.1  4.8   550.0 -35.2 -6.0                             72   595.0   657.1   62.1  10.4  648.6 53.6  9.0                              75   639.1   680.8   41.7  6.5   662.8 23.6  3.7                              81   658.6   627.5   -31.1 -4.7  649.7 -8.9  -1.3                             84   810.3   720.1   -90.2 -11.1 784.3 -26.0 -3.2                             87   817.7   723.1   -94.6 -11.6 795.0 -22.7 -2.8                             ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    WATER    Model P2        Model PG                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        87   510.9   544.8   34.0  6.7   502.9 -8.0  -1.6                             84   514.1   538.5   24.4  4.7   505.3 -8.8  -1.7                             75   584.7   560.5   -24.2 -4.1  578.4 -6.3  -1.1                             72   587.1   554.6   -32.5 -5.5  567.1 -20.0 -3.4                             81   590.1   607.9   17.7  3.0   594.0 3.9   0.7                              63   595.2   586.5   -8.7  -1.5  590.3 -4.9  -0.8                             54   651.9   658.6   6.8   1.0   653.9 2.1   0.3                              78   671.6   647.7   -24.0 -3.6  671.9 0.3   0.0                              57   690.7   665.9   -24.9 -3.6  678.8 -11.9 -1.7                             69   709.6   681.4   -28.2 -4.0  702.3 -7.3  -1.0                             66   738.3   710.4   -27.9 -3.8  738.0 -0.2  0.0                              60   743.4   735.4   -8.0  -1.1  737.8 -5.6  -0.8                             33   748.7   744.8   -3.9  -0.5  754.9 6.2   0.8                              48   752.5   755.6   3.1   0.4   755.0 2.5   0.3                              27   776.2   796.5   20.3  2.6   767.3 -8.9  -1.1                             18   787.6   837.4   49.8  6.3   813.8 26.2  3.3                              51   809.2   763.2   -46.0 -5.7  792.9 -16.3 -2.0                             21   817.0   844.7   27.8  3.4   836.9 19.9  2.4                              39   835.0   836.8   1.8   0.2   823.3 -11.7 -1.4                             12   837.0   891.5   54.4  6.5   859.7 22.7  2.7                              36   846.6   846.9   0.3   0.0   830.6 -16.1 -1.9                             42   850.6   841.2   -9.4  -1.1  835.7 -14.9 -1.8                             24   869.1   909.0   39.9  4.6   868.7 -0.4  0.0                              30   875.5   902.0   26.5  3.0   858.7 -16.8 -1.9                             9    874.3   986.2   11.9  1.2   981.0 6.6   0.7                              ______________________________________                                    

                  TABLE 17                                                        ______________________________________                                                 mud density not used                                                                          mud density input                                    Z        Model P1        Model PE                                             Sam-                 Error,                                                                              Error,      Error,                                                                              Error,                           ple  Actual  Pred.   g/L   %     Pred. g/L   %                                ______________________________________                                        9    8.40    8.50    0.10  1.14  8.72  0.31  3.72                             12   10.61   10.15   -0.46 -4.33 10.74 0.13  1.23                             18   11.85   11.75   -0.10 -0.87 11.91 0.06  0.50                             21   12.46   12.60   0.13  1.08  12.22 -0.24 -1.93                            24   12.60   12.60   0.00  0.01  12.45 -0.15 -1.17                            27   14.15   14.61   0.46  3.25  13.72 -0.43 -3.02                            30   14.29   14.27   -0.02 -0.11 13.91 -0.38 -2.64                            33   15.63   15.88   0.26  1.66  15.44 -0.18 -1.16                            36   16.10   16.61   0.51  3.18  15.85 -0.25 -1.55                            39   16.92   17.40   0.48  2.83  16.93 0.01  0.04                             42   17.48   17.71   0.23  1.29  17.95 0.47  2.67                             48   18.82   18.88   0.06  0.31  18.92 0.10  0.54                             51   19.60   19.88   0.28  1.43  19.74 0.14  0.71                             54   20.12   19.97   -0.14 -0.72 20.60 0.48  2.38                             57   20.91   20.86   -0.05 -0.25 21.47 0.56  2.66                             60   21.79   21.70   -0.10 -0.45 21.73 -0.07 -0.31                            63   22.48   22.44   -0.04 -0.20 22.55 0.07  0.31                             66   23.42   23.37   -0.05 -0.21 23.45 0.04  0.15                             69   23.99   24.29   0.30  1.24  24.38 0.39  1.61                             72   24.46   24.40   -0.06 -0.23 24.39 -0.07 -0.27                            75   25.05   25.39   0.34  1.36  25.30 0.25  1.00                             78   26.06   26.56   0.50  1.91  26.26 0.20  0.76                             81   26.38   26.64   0.25  0.95  26.59 0.20  0.76                             84   26.42   26.57   0.15  0.57  26.42 0.00  -0.01                            87   27.34   27.49   0.15  0.53  27.24 -0.10 -0.36                            ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        SG                                                                                       Model P2                                                           Sample   Actual  Pred.      Error, g/L                                                                            Error, %                                  ______________________________________                                        9        1.05    1.03       -0.01   -1.16                                     24       1.28    1.20       -0.08   -6.25                                     12       1.29    1.18       -0.11   -8.40                                     30       1.33    1.25       -0.08   -5.74                                     21       1.34    1.31       -0.03   -2.45                                     18       1.38    1.30       -0.07   -5.18                                     36       1.41    1.40       -0.01   -0.73                                     39       1.43    1.43       0.00    -0.14                                     42       1.43    1.44       0.00    0.32                                      27       1.44    1.40       -0.05   -3.31                                     33       1.52    1.55       0.03    1.83                                      51       1.57    1.65       0.08    5.00                                      48       1.61    1.59       -0.02   -1.24                                     60       1.73    1.75       0.02    0.93                                      66       1.79    1.85       0.05    3.02                                      57       1.82    1.84       0.02    1.34                                      54       1.84    1.83       -0.02   -0.82                                     69       1.88    1.93       0.05    2.48                                      63       1.99    1.99       0.01    0.34                                      78       2.03    2.07       0.04    1.83                                      72       2.10    2.11       0.02    0.74                                      75       2.13    2.16       0.03    1.57                                      81       2.17    2.14       -0.03   -1.51                                     84       2.34    2.25       -0.09   -3.76                                     87       2.38    2.29       -0.10   -4.01                                     ______________________________________                                    

We claim:
 1. A method of analyzing a drilling fluid comprising solidssuspended in a liquid phase, the method comprising subjecting a sampleof the fluid to an X-ray fluorescence (XRF) analysis technique so as toderive a spectrum therefrom; analyzing the spectrum to identify a peakof intensity I_(HGS) in the spectrum due to the presence of a componentof the high gravity solids fraction of the sample and a peak ofintensity I_(Co) due to Compton scattering and determining the ratioI_(HGS) /I_(Co) ; and using data from the derived spectrum, the ratioI_(HGS) /I_(Co) and a calibration model to calculate the amount of saidcomponent and liquid phase in the sample.
 2. A method as claimed inclaim 1, further including the step of calculating the specific gravitySG of the sample.
 3. A method as claimed in claim 1, comprisingmeasuring the SG of the sample and using the measured SG in thecalculation.
 4. A method as claimed in any preceding claim, comprisingcalculating the amount of low gravity solids in the sample.
 5. A methodas claimed in any of claims 1-3, comprising calculating the averageatomic number Z of the sample.
 6. A method as claimed in claim 4,comprising measuring the amounts of salts in the sample and using themeasured amount to calculate the amount of low gravity solids in thesample.
 7. A method as claimed in any of claims 1-3, wherein the sampleis irradiated from a single source.
 8. A method as claimed in any ofclaims 1-3, wherein the component of the high gravity solids fractioncontains barium.
 9. A method as claimed in any of claims 1-3, whereinthe sample is irradiated from two different sources.
 10. A method asclaimed in claim 9; wherein the spectrum produced by irradiation with afirst source is used to calculate the amount of said component of thehigh gravity solids fraction of the sample which in turn is usedtogether with the spectrum from a second source to calculate the amountof other components in the sample.
 11. A method as claimed in any ofclaims 1-3, wherein the liquid phase is water.
 12. A method as claimedin any of claims 1-3, wherein the drilling fluid is oil-based, theliquid phase comprising oil and brine.
 13. A method of analyzing theconcentration of one or more polymers in a drilling fluid comprisingobtaining the IR spectrum of the sample, subjecting the sample to XRFanalysis by a method as claimed in any of claims 1-3, to determine theconcentration of minerals in the sample, comparing the IR spectrum witha calibration model corrected with the results of the XRF analysis todetermine the concentration of polymers in the sample.
 14. A method asclaimed in any of claims 1-3, wherein the calibration model isconstructed from analysis of various fluids of known composition.
 15. Amethod as claimed in any of claims 1-3, which utilizes a regressiontechnique to relate the measurements to the calibration model.
 16. Amethod as claimed in claim 15, wherein the regression technique is apartial least squares method.
 17. A method as claimed in any of claims1-3, wherein the XRF technique provides spectral information of sulfur,chlorine, potassium, chromium and barium in the sample.
 18. A method asclaimed in claim 9, wherein the sources are Am 241 and Fe
 55. 19. Amethod as claimed in any of claims 1-3 including determining calciumconcentration, density and optionally oil/water volume ratio.
 20. Amethod as claimed in claim 19, wherein calcium concentration isdetermined by EDTA titration or by use of an ion-selective electrode.21. A method as claimed in claim 20, wherein the sample is analyzed togive barite content, LGS not containing Ca, LGS containing Ca, solubleK, Cl, water content and oil content.
 22. A method as claimed in claim10, wherein the first source is used to give an approximatedetermination of the Ba content of the fluid which is then used in theanalysis of the second source for Ba and other fluid components andphysical properties, at least one of the physical properties determinedfrom the second source being used in a further analysis of the firstsource response to improve the determination of Ba.
 23. A method asclaimed in claim 12, wherein the density of the brine is alsocalculated.
 24. A method as claimed in claim 12, wherein the wateractivity of the brine is also calculated.
 25. A method as claimed inclaim 23, wherein the water activity of the brine is also calculated.